Allergy
An allergy is an immune reaction of the organism against a substance that is generally innocuous to the host, which is manifested by characteristic signs and symptoms when the host is exposed to it (by inhalation, ingestion or contact cutaneous). Allergy has long been considered equivalent to hypersensitivity (an older term) and therefore mistakenly regarded as an exaggerated immune reaction to a substance. But "allergy" is the clinical expression of the body's normal immune response mechanisms against potential invaders; and the error is not in the type of response or its intensity, but in the objective, which does not constitute any threat. The final consequence of this error of the immune system is the disease of the host, caused by the collateral effects suffered by the tissues, where the immune system tries to defend itself against this innocuous substance. The clinical manifestations of this disease are diverse, since they depend on the causative substance and the affected organ. Currently, more than a third of the world's population has some disease of allergic origin.
Allergic diseases include rhinitis, food allergies, dermatitis, allergic asthma and anaphylaxis. For almost 100 years, allergology has been the medical specialty that deals with the study, diagnosis and treatment of this group of diseases and the medical professionals who perform it are called allergists (Spain) or allergists (South America).
Food allergy is often confused with food intolerance. Food intolerance is distinguished from allergies in that the latter cause a response from the immune system and intolerances are generally due to enzyme deficiencies, which prevent proper nutrient metabolism. A special case is celiac disease, usually referred to as an "allergy" or an "intolerance" to gluten, when in reality it is neither an allergy nor a simple intolerance. It is an autoimmune multi-organ disease, in which gluten causes an abnormal response from the immune system, which mistakenly attacks and damages the intestine and any organ or bodily tissue.
Allergies usually appear at any age, since babies can feed you with foods that are not yet suitable for their organism, due to their young age, such as shellfish.Terminological problems
The term «allergy» was coined in response to a new conception of the immune system and as a solution to a terminological problem (see History section), but, paradoxically, throughout its history it has given rise to many conceptual problems that they still persist today and have endowed the term with ambiguity.
In October 2003, the World Allergy Organization (WAO) Nomenclature Revision Committee updated the expert consensus statement on allergy terminology published in 2001 by the European Academy of Allergology and Clinical Immunology (EAACI), with the aim of eliminating ambiguity. The report first defined the broad term "hypersensitivity" as "objectively reproducible symptoms or signs initiated by exposure to a defined stimulus at a dose tolerated by normal persons." Hypersensitivity could be divided into a non-allergic type, when no immune mechanism could be demonstrated, and an allergic type, when such a mechanism could be demonstrated. Therefore, it is very important to always record, when referring to this type of reaction, the mechanism involved: IgE, IgG, IgM, immunocomplex or cellular antibodies. The classic diseases considered allergic are those mediated by IgE antibodies, and for this reason today one should always write when consigning them “IgE-mediated allergic hypersensitivity” rather than simply “allergy”. But there are other diseases due to allergic hypersensitivity produced by other mechanisms, so the optimal way to designate these diseases will be by specifying their immune mechanism. To define the types of allergic hypersensitivity, the Gell and Coombs classification of 1963 is still valid.
But despite these international efforts, the term "allergy" is still used today in many settings, both in the sense of allergic hypersensitivity reaction of any type and IgE-mediated allergic hypersensitivity (or type I in the Gell and Coombs classification). For example, in the field of respiratory diseases and latex allergy, "allergy" always refers to IgE-mediated diseases, but in the field of food allergy, drug allergy, and skin diseases, "allergy » can be any type of hypersensitivity reaction. For this reason it is very important to insist on the respect of the terminological norms of the WAO and the EAACI.
Classification
The diseases that are usually considered, generally, under the term "allergy" (because they are mediated by IgE-type antibodies or related) and that in fact allergists treat more frequently (although not exclusively), are the following:
Asthma
Allergic asthma is called when it is caused by immunological reactions, which in most cases are initiated by IgE-type antibodies, so it can also be called IgE-mediated allergic asthma. Asthma is a disease of the respiratory system characterized by chronic inflammation of the airways, whose clinical manifestations are heterogeneous and variable over time and consist of wheezing, respiratory distress, chest tightness, and cough.
The origin of the disease is complex and involves inflammation, intermittent obstruction, and hyperreactivity (increased bronchoconstrictor response) of the airways. The presence of edema and mucus secretion contribute both to obstruction and increased reactivity. The disease can have an acute, subacute, or chronic course, depending on the frequency, duration, and intensity of its clinical manifestations.
The manifestations of asthma occur in response to numerous triggering stimuli, both endogenous (internal to the person) and exogenous (from the environment). The underlying mechanisms include direct stimulation of the smooth muscles of the bronchial tree and indirect stimulation for cells of their own to secrete active substances that produce the inflammatory reaction and bronchoconstriction. Among these triggering stimuli are exposure to an inappropriate environment (cold, humid or with allergens), exercise or exertion, and reactions to food or other substances as a consequence of increased intestinal permeability. Viral and bacterial illnesses of the upper respiratory tract and emotional stress can worsen symptoms.
Symptoms of asthma are wheezing, shortness of breath, tightness in the chest, and unproductive coughing at night or early in the morning. These symptoms occur with different frequency and intensity, interspersed with asymptomatic periods where most patients feel well. Conversely, when asthma symptoms worsen, an asthma attack occurs. It can be a short-term respiratory crisis, or prolonged with daily asthmatic attacks that can persist for several weeks. In a severe crisis, the airways can close, preventing the lungs from performing their gas exchange function (taking in oxygen and expelling carbon dioxide) to the point that vital organs cannot function either. In these cases, the asthmatic attack can cause death.
There are multiple therapeutic alternatives to avoid symptoms, control and alleviate them, as well as to recover from asthma attacks, being their use through inhalers the most frequent.
Rhinitis
Allergic rhinitis is called when the typical symptoms (nasal congestion, runny nose, sneezing, or nasal itching) are the result of a hypersensitivity reaction —mostly IgE—, so it can also be called mediated allergic rhinitis by IgE.
In turn, based on the duration of the symptoms, it is subdivided into intermittent and persistent; seasonal allergic rhinitis refers to seasonal episodes, such as pollen-induced allergic rhinitis. In relation to the effect of the symptoms on activities of daily living and sleep, it can be called mild or moderate-severe.
All other forms of rhinitis are classified as non-allergic rhinitis.
Conjunctivitis
The frequent association of IgE-mediated allergic conjunctivitis with allergic rhinitis makes the term allergic rhinoconjunctivitis the most appropriate for its name. In addition to IgE-mediated conjunctivitis, allergic contact conjunctivitis may occur, which involves mechanisms of Th1 lymphocyte activation.
Other forms of conjunctivitis are classified as non-allergic conjunctivitis, which often accompanies non-allergic rhinitis.
Dermatitis
It has been difficult to establish consensus regarding the nomenclature of the dermatological aspects of allergy. Dermatitis is the generic term to define a local inflammation of the skin.
Eczema
What is generally known as eczema/atopic dermatitis syndrome is not a single entity, but a sum of several skin disorders with certain common clinical features. Therefore, the term eczema is more appropriate. In children and young people with an atopic constitution, the underlying inflammation is dominated by IgE antibodies, and the term atopic eczema is used when IgE-mediated sensitization is demonstrated. In some countries, the corresponding term would be atopic dermatitis, although it is not fully consistent with the new nomenclature.
When the immune mechanism of eczema is not clear, the disease is called eczema.
Differentiation between atopic eczema and eczema generally seems to be of great prognostic importance. Nonatopic children with eczema have a lower risk of developing asthma in adolescence than atopic children with eczema. Eczema without any sign of an atopic constitution is common in preschool children, with a recently estimated prevalence of 45-64%, but even in adults, figures as high as 40% have been reported. However, non-atopic eczema can progress to atopic eczema.
Contact dermatitis
Contact dermatitis refers to a local inflammatory reaction of the skin, caused by direct contact with low molecular weight chemicals or irritants. When these reactions are mediated by immunological mechanisms, mainly by Th1 lymphocytes, it is called allergic contact dermatitis.
Some typical allergens are: nickel, fragrances, chromium ions, preservatives, and urushiol, from the poison ivy plant. If exposure occurs orally it is called systemic allergic contact dermatitis. When immune mechanisms are not involved, it is called non-allergic contact dermatitis or irritant/toxic contact dermatitis.
A subgroup of contact dermatitis, protein contact dermatitis, is probably an IgE-associated reaction caused by absorption of proteins through damaged skin, correctly termed IgE-associated protein-associated allergic contact dermatitis.
Other forms of dermatitis
They include nummular dermatitis and photosensitive dermatitis, but also diseases classified as eczema: dyshidrotic eczema and seborrheic eczema.
Hives
Urticaria is characterized by the development of erythematous, pruritic plaques that come and go over minutes to hours, sometimes several days. When it is mediated by an immune mechanism it is called allergic urticaria, commonly related to IgE, which is why it is called IgE-mediated urticaria. IgE-mediated urticaria is usually the acute form; Chronic urticaria is usually due to other immune mechanisms.
Urticaria has been described due to topical contact with allergens, as occurs in allergy to latex due to the use of gloves or as a consequence of dog licking in people allergic to these animals. In these cases it is called allergic contact urticaria and may be IgE mediated. Autoantibodies may be involved in certain types of chronic urticaria and are therefore a variety of allergic urticaria.
Food allergy
It is classified into three groups, according to the mechanism of the allergic response:
- Mediated by IgE (classic). Symptoms appear shortly after the ingestion of the food involved (seconds or minutes). It can produce an anaphylactic crisis, which can be fatal without immediate treatment. It is triggered by an immune system reaction, which produces an antibody called immunoglobulin E (IgE). It is diagnosed by skin or blood test.
- Not mediated by IgE. It is characterized by an immune response that does not involve immunoglobulin E. It can happen several hours after eating (up to 72 hours) and there are no tests to detect it, which makes it very difficult to recognize and diagnose it. This is done through a diet to eliminate suspicious foods.
- Mediated by IgE and not mediated by IgE. A combination of the two previous types
Any food is susceptible to cause allergies, although the most commonly implicated are milk, soybeans, wheat, peanuts, tree nuts, fish and shellfish.
Increased intestinal permeability has now been shown to play a key role in the development of food allergies. The two most potent factors causing increased intestinal permeability are certain intestinal bacteria and gluten, independently of genetic predisposition, that is, both in celiacs and non-celiacs.
Allergy to medications
They are all adverse reactions to drugs in which immune mechanisms involved are demonstrated. Adding adjectives such as immediate and delayed describes the time until the onset of symptoms, and this is usually related to the type of immune mechanism involved (IgE-mediated or lymphocyte-mediated, respectively). The immune mechanisms of drug allergy are sometimes very difficult to identify. One of the most frequent is usually to antibiotics, mainly penicillin and its derivatives (ampicillin, amoxicillin, etc.).
Allergy to insect bites
Immune-mediated hypersensitivity to insect venom or saliva is called venom or saliva allergy, as in the case of bee venom allergy. It can be called IgE-mediated venom allergy if one wants to emphasize the role of IgE. The sheer amount of venom allergen in a single bite can be compared to years of inhaling pollen allergens. Other reactions are grouped under the term non-allergic insect venom hypersensitivity.
Anaphylaxis
The term anaphylaxis is used differently by doctors around the world. Anaphylaxis is a severe systemic or generalized hypersensitivity reaction, life-threatening, induced by various stimuli and of sudden onset, caused by the systemic release of histamine and other pharmacological mediators. When the reaction is mediated by an immunological mechanism, be it IgE, IgG, or related to the complement system, it is called allergic anaphylaxis. If it is IgE-mediated, it may be called IgE-mediated allergic anaphylaxis. Anaphylaxis from any non-immune cause is called non-allergic anaphylaxis.
History
Allergic diseases have been known to have existed since ancient times, but their mechanisms did not begin to be rigorously studied until the mid-19th century with the rise of hay fever in countries beginning to industrialize and in the early 19th century. XX with the discovery of the mechanisms of immunity.
But the term "allergy" was not coined until 1906. The author was the Viennese pediatrician Clemens von Pirquet and he intended it to replace the old Latin term "immunity". Von Pirquet warned that the immune system, Until then considered exclusively protective, it could harm the host it was trying to protect, either as a side effect in its fight against infectious microorganisms or by choosing innocuous targets. For this reason, it was inappropriate to speak of "immune reactions" (whose Latin etymology refers to protection) and it would be better to use a term like "allergy" that simply implied a change in reactivity, that is, the ability of the immune system to recognize an infection. substance and react to it. The result of that reactivity could be protective, that is, the host would not show any symptoms in response to that substance (what would be true immunity), or cause symptoms and disease (what would be called hypersensitivity); between the two non-exclusive extremes there would be a whole spectrum of responses from the host.
But the evolution of the word allergy followed a very different path to the wishes of its creator and in a very few years «allergy» was identified with all those harmful reactions of the immune system caused by its recognition of innocuous targets. But the word was very attractive to the medical community and the general public and already from the 30s of the 20th century there were clinics, medical journals and societies dedicated to allergies throughout Europe and the United States, this expansion of the term helped of course the growing prevalence of allergic diseases in these industrialized societies (see exhaustive analysis of this historical and conceptual evolution in)
Epidemiology
The prevalence of allergic diseases is experiencing a continuous increase worldwide, with an estimated percentage of the population affected at 30-40%. A high proportion corresponds to young people, which implies that the burden of allergic diseases will be higher when these subjects reach adulthood. Currently, among school-age children, rates of sensitization to one or more common allergens approach 40-50%.
Likewise, the increase in air pollution and the ambient temperature that is being experienced, causes pollen counts to rise, as well as the presence of insects and fungi associated with allergic diseases.
More than 50% of asthma cases in adults and around 80% in children are of allergic origin, with a clear increase in its prevalence.
Allergic rhinitis is present in 10-30% of the population.
Adverse drug reactions affect approximately one tenth of the world's population, of which 10% correspond to unpredictable hypersensitivity reactions. Medications can be responsible for up to 20% of anaphylaxis deaths.
The presence in the general population of specific IgE antibodies to Hymenoptera venom is high, although only a part of these people develop a systemic reaction. However, up to 50% of people without a prior documented history of a systemic reaction experience a fatal reaction.
Occupational allergic diseases have a high prevalence, although they are generally underestimated by patients and professionals. Allergic contact dermatitis is one of the most common occupational diseases. Occupational asthma accounts for 15% of asthma in adults.
IgE-mediated sensitization to foreign proteins in the environment affects up to 40% of the population. This sensitization is strongly associated with exposure to proteins derived from pollen, dust mites, fungi, and cockroaches.
Etiology
It is generally accepted that the development of diseases of immune origin is due to the interaction between specific susceptibility genes and certain environmental factors. In the case of allergies, antigens such as pollens, house dust mites, food, molds, animal dander, medicines, etc. However, less than 10% of people with higher genetic susceptibility develop the disease, indicating the existence of a strong trigger that also affects the progress and prognosis of the disease. disease. In addition to genetic predisposition and exposure to antigens, the third key element required is the loss of the protective function of mucosal barriers, mainly the intestinal and pulmonary mucosa. The genetic predisposition to present allergic reactions is called atopy, defined as the personal or familial tendency to produce IgE antibodies in response to allergens. Therefore, atopy does not mean the presence of allergic disease (rhinitis, asthma, food allergy, dermatitis, etc.), but a greater tendency to suffer from it.
Increased intestinal permeability
The intestine is the largest mucosal surface of the body. When healthy, it acts by allowing nutrients to pass through the blood and blocking potentially harmful substances. However, when its mucosa is damaged and intestinal permeability increases, substances that should not pass (toxins, chemicals, microorganisms, macromolecules and incompletely digested food) pass into the blood. Depending on the genetic predisposition of each person, this can lead to the development of allergies and a large number of other diseases, such as autoimmune and inflammatory diseases, infections or cancers, both intestinal and in other organs.
The two most potent triggers that cause increased intestinal permeability are certain intestinal bacteria and gliadin (protein fraction of gluten), regardless of genetic predisposition, that is, both in celiac and non-celiac patients. Others possible causes are prematurity, exposure to radiation, and chemotherapy. Unrecognized and untreated celiac disease and non-celiac gluten sensitivity, as they usually occur without digestive symptoms or these are mild, are frequently associated with natural processes. immuno-allergic, such as asthma, rhinitis and pharyngoamigdalitis, among others, which may be the only symptoms of its presence. Approximately 20% of people with non-celiac gluten sensitivity without treatment present, associated with gluten intolerance, IgE-mediated allergies to one or more inhalants, foods, or metals, the most common of which are dust mites, gr amines, dog or cat hair, fish or nickel.
The discovery of the role of intestinal permeability upsets traditional theories and suggests that these processes can be stopped if the interaction between genes and environmental triggers is prevented, through the restoration of intestinal barrier function.
Lung barrier defects
Airway epithelial cells are the first line of mucosal immunity. These cells form a barrier to the outside world and, according to mounting evidence, a malfunction of this epithelial barrier is a hallmark of airway inflammation in asthmatic patients. It has been shown in various studies in the skin and gastrointestinal tract that increased permeability is required to initiate the immune response, although how this applies to lung mucosal immunity is unclear.
Hygiene hypothesis
The essence of the "hygiene hypothesis" holds that the increasing incidence of diseases of immune origin is due, at least in part, to lifestyle and environmental changes that have caused us to reduce contact with microorganisms. This theory has been shown to be insufficient and has now been replaced by the old friends theory., salmonella, etc.) that have co-evolved with humans for millions of years have since then carried out functions of instruction of the immune system necessary for the defense of infectious microorganisms and for the tolerance of innocuous substances, for which reason its absence in today's modern world has given rise to immune disorders such as allergy and autoimmune diseases (old friends theory). Epidemic viruses such as influenza, measles or mumps, causes of infection that are so frequent today, would not have such an immune-instructing effect since they have only been associated with humans for 10,000 years.
Pathogenesis
In subjects with a genetic predisposition, specific IgE antibody molecules are produced against a certain allergen, which tend to bind to its high-affinity receptor, present on the membrane of mast cells and, to a lesser extent, basophils., and its low-affinity receptor, which is found on many other cells. Subsequent contact with the allergen will produce a release of mediators capable of producing the characteristic symptoms of allergic diseases of greater or lesser intensity depending on the load released. The allergic reaction is called immediate hypersensitivity, because, in general, it appears quickly (within the first hour) after contact with the antigen (in this case, more properly allergen).
Mast cell mediators are classified as preformed or primary and secondary or synthesized de novo. The former are responsible for the early response (first hour after antigenic exposure) and the latter for the late response (appears more than an hour after the stimulus). These mediators cause vasodilation with increased vascular permeability, smooth muscle contraction, platelet aggregation, eosinophilic inflammatory infiltrate, increased mucus secretion, and stimulation of sensory nerves.
The indisputable protagonist of the late phase is the appearance of an inflammatory reaction. This final common pathway of many allergic reactions is facilitated by the activity of late-phase mast cell mediators. This late inflammatory phase is responsible for epithelial damage, and the appearance of cellular infiltrates and fibrin deposits in the target organ, which make the hypersensitivity reaction chronic.
Some subjects produce specific IgE antibodies against various allergens, but, nevertheless, they do not present any type of clinical manifestation when exposed to them. In such a case, the subject is said to have a "subclinical sensitivity" to the allergen in question, and the mechanisms that prevent the disease from occurring are unknown.
Sensitization to certain allergens is enhanced by the presence of adjuvants, for example aluminum hydroxide, certain oils or bacterial debris.
Clinical picture
Symptoms manifest clinically depending on the organ in which the released mediators act, which can produce:
- In the skin: eczema, erythema, angioedema (swelling) and pruritus (short), as well as habony lesions (screws) of the urticaria and/or dermatitis.
- In bronchus: bronchoespasm, inflammation and increased secretions, characteristic of asthma.
- In the nasal mucosa: inflammation and pruritus, which triggers sneezing, as well as increase of mucous secretion, proper of rhinitis.
- In the eyes, conjunctivitis and queratitis.
- In the digestive tract: diarrhea, vomiting and abdominal pain, symptoms that appear in the food allergy.
- When contact with the allergen occurs by general means (such as inoculation of the poison of hymenopter after the bite of bee or wasp, administration of a medicine or intake of food), symptoms may appear in distant organs or even a severe involvement of several organs (urticaria, bronchoscopy, arterial hypotension, tachycardia), which is known as an anaphylaxia.
- Other symptoms include interstitial pneumopathy, eosinophil pneumopathy, sinusitis, epistaxis, anosmia, anemia, thrombopenia, leucopenia and eosinophilia.
Atopic eczema (or atopic dermatitis) is often the first manifestation of the atopic patient, especially in children, and early intervention may offer an opportunity to prevent or stop the so-called allergic march: progressive onset of various allergic diseases (food allergy, rhinoconjunctivitis, asthma).
Allergy should not be confused with intolerance. Intolerance (such as the one that can appear to certain foods) is distinguished from allergy in that the latter is caused by an altered response from the immune system, while intolerances do not involve the immune system.
Allergic attack
Severe allergic attacks may be accompanied by:
- Anaphylactic shock: Acute and extreme allergic reaction that can be lethal.
- Quincke's edema, or angioedema.
- Vets, syncopes, fading, nausea.
- Inflammation of lips, eyelids, fingers, pruritus or itching throughout the body.
- Respiratory difficulty (disnea).
- Uncomfort or decay.
- Urticaria (it is caused by bites, medicines, latex, etc.).
- Sneezing: allergic rhinitis (or "female fever").
Since allergies are an abnormal response of the immune system, it is considered to exist under four possible aspects:
- Immediately: It depends on the antibodies already mentioned of type E (IgE) (in the urticaria and edema of Quincke).
- Cyto-toxic: With IgG type antibodies.
- Complex immune: Equally linked to IgG, though forming immune complexes.
- Retardada: Lying to cell inflammation as is the allergy responsible for eczema.
Diagnosis
To diagnose an allergic disease, a correlation must be established between the observed symptoms, the triggering allergen and the involvement of the immune system. It should begin with a medical history of the patient, considering the family history, and a physical examination. In many cases, a series of complementary tests must be used to demonstrate the presence of the suspected allergen.
Health care professionals can use test results to identify specific allergy triggers that may be contributing to symptoms. With this information, used in conjunction with the physical examination and medical history, the doctor can diagnose the cause of the symptoms and design personalized treatment to help the patient experience improvement. A negative result can help the doctor rule out allergies so other possible causes can be considered. Ruling out allergies is just as important as confirming their existence, to limit both avoidance measures and unnecessary worry and negative social impacts.
The most frequently used diagnostic method are skin tests (known as “skin tests” or Prick test) and are very useful to help confirm or rule out allergies and consequently reduce adverse reactions and limit avoidance and unnecessary medications. Correct diagnosis, counseling, and avoidance advice based on valid allergy test results will help reduce both the incidence of symptoms and the use of medications, improving quality of life.
As a general rule, all children with persistent/recurring/severe “allergy symptoms,” as well as those individuals who need ongoing treatment, should have allergy testing, regardless of the child's age. signs and symptoms may be related to:
- The skin, such as pruritus, erythema, acute urticaria or angioedema.
- The gastrointestinal system, such as swelling of the lips or tongue, nausea, spasmodic abdominal pain, diarrhea, vomiting.
- The respiratory system, such as nasal pruritus, sneezing, congestion, coughing, chest compression, wheezing, shortened breathing.
- Signs or symptoms of anaphylaxis or other systemic allergic reactions.
Guidelines issued by the National Institute for Health and Clinical Excellence (NICE) in February 2011 provide best practice advice in treating children and adolescents with possible food allergies, up to 19 years of age. The NICE guidelines recommend that all children and adolescents with possible IgE-mediated food allergies undergo allergy testing, such as testing for specific IgE antibodies.
Blood test
A blood test for allergy diagnosis is quick and easy and can be ordered by a licensed health professional such as an allergist, family doctor or pediatrician. Although they can be used for any allergen, they are especially useful in the diagnosis of food allergy. Unlike the traditional prick test, performing a blood test does not depend on age, skin condition, medications, symptoms, disease activity, or pregnancy. Both adults and children of any age can undergo an allergy blood test. For babies and very young children, a single prick blood test is usually more bearable than multiple tests.
An allergy blood test can be ordered through most labs. A sample of the patient's blood is sent to a laboratory for analysis and the results are delivered in a matter of days. With a single blood sample it is possible to identify multiple allergens. The doctor studies the test results and, taking into account the patient's symptoms and medical history, determines whether the patient has allergies.
The NIH guidelines state that: “Specific IgE tests are useful for the identification of potential trigger foods for IgE-mediated food-allergic reactions and specified breakpoints, defined by a positive predictive value of 95%, may be more predictive with respect to clinical reactivity in certain populations than prick tests. They then indicate that: “specific IgE tests are useful for detecting the presence of IgE antibodies, which indicate allergic sensitization. Assays based on the use of fluorescently labeled antibodies have comparable sensitivity to skin prick tests, and absolute levels of specific IgE antibodies can be correlated with the likelihood of clinical reactivity compared to oral challenge to identify food triggers. of IgE-mediated allergy”.
Blood tests for the diagnosis of allergies, such as those of ImmunoCAP, are performed without variations in the procedure, and the results are of excellent standardization. On the contrary, the reagents and methods used for the prick tests are not standardized. In "Evidence-based Allergy Diagnostic Tests", Portnoy states that:
“Although skin tests are both sensitive and specific, they are also highly irregular. The results of a person's skin tests can vary depending on the test performer and tend to vary depending on the time of day and season of the year, the area of the body the test is performed on, the device used, the source of the extract and the concentration. Unfortunately, traditional customs prevail in the procedures followed during the performance and interpretation of skin tests. For example, techniques may vary depending on where the physician trained and who provided the training; some sites do only prick tests, while others only do intradermal tests, and there are others where they do both.”
Tests
The NIH guidelines on the diagnosis and treatment of food allergy and asthma recommend either an allergy blood test or a prick test to reliably diagnose allergic sensitization. Both tests are highly accurate and have similar diagnostic value with respect to sensitivity and specificity. Advances and improvements in allergy blood test technology have improved the sensitivity and accuracy of the test to such an extent that the blood test is considered for allergy and the puncture test are interchangeable.
In an allergy blood test, a sample of the patient's blood is sent to a laboratory. The doctor studies the test results, which help him determine if the patient has allergies.
In the prick test, several drops of a solution containing possible allergens are placed on the patient's skin, and a series of scrapes or needle pricks are made to allow the solution to penetrate the skin. The doctor looks for pronounced reactions such as red bumps or bumps to help determine if the patient has allergies.
According to the NICE guidelines, the prick test and the blood test are equally economical and the evidence on health economics shows that both the IgE antibody test and the prick test are economical compared to not performing them of tests. Plus, earlier and more accurate diagnoses save money due to fewer GP visits, secondary care referrals, misdiagnosis, and ER visits.
Follow-up
Allergy evolves over time and patients can outgrow allergies and develop new ones. Frequent diagnostic testing for relevant allergens is recommended, as it provides information on whether and how the patient's treatment can be changed to improve health and quality of life. The need and frequency of its performance is highly variable, depending on the patient and the allergen involved and must be decided by the specialist doctor. An annual test is generally the recommended practice to determine if allergy to milk, egg, soy and wheat has been overcome and the interval between tests is extended to 2 or 3 years for allergy to peanuts, the fruits of tree shell, fish, and crustaceans. Results of follow-up tests can guide decision regarding the feasibility and safe timing of introducing or reintroducing allergy-triggering foods into the diet. Reassessment interval depends on the specific food trigger of the allergy, the age of the patient and the medical history.
Genetic studies
Genetic studies can be carried out on the relationship established between different loci and some clear symptoms of this disease. For this, genome-wide association studies or GWAS or eQTL or expression studies are carried out. The first is the most used as it is an analysis of genetic variation throughout the entire human genome with the aim of identifying its association with an observable trait, thus it can be concluded that the appearance of one to several SNPs or a deletion appears in a pathological phenotype.[citation needed]
Treatment
The treatment of these patients should be based on the concept that allergic diseases are caused by an altered immune reaction to an external agent and are, in fact, chronic diseases that present exacerbations. Therefore, exclusively symptomatic treatment of acute manifestations should be avoided. A correct treatment must include three pillars: Avoidance of the allergen, pharmacological treatment and modification of the altered immune response.
Allergen Avoidance
It should be the first pillar of treatment, especially in situations where the allergen can be avoided: food and medication. It must be taken into account that foods or medications from the same family or similar chemical structure can cause symptoms and should also be avoided. Inhaled allergens (mites, pollens, fungi, animal epithelia) are more difficult to avoid and require specific measures for each of them.
Pharmacological treatment
It is performed on the target organ and must include maintenance treatment (generally anti-inflammatory) and treatment of acute symptoms that may appear after intense contact with the allergen. Pharmacological treatment varies depending on the affected organ: the use of antihistamines in allergic rhinoconjunctivitis is common, as well as local (nebulized) glucocorticoids, which achieve a powerful anti-inflammatory effect with few adverse effects. Local (inhaled) glucocorticoids are also used as maintenance drugs in asthma, although they are frequently associated with bronchodilators. Other drugs such as antileukotrienes are also used, which also produce an anti-inflammatory effect. Antihistamines are also used in skin lesions, although with variable efficacy. The simultaneous presence of severe and generalized allergic symptoms (choking, hypotension, tachycardia, angioedema, urticaria) after ingesting a food or administering a medication to which the patient is allergic (anaphylaxis) requires intensive treatment that, on many occasions will require the use of intramuscular adrenaline. The use of adrenaline may also be necessary after an anaphylactic reaction after a hymenopteran (wasp or bee) sting in sensitive patients.
For Allergic Asthma, four types of treatment are mainly used:
- (a) Broncodilators o simpaticomymetics beta-2: they act relaxing the smooth muscle surrounding the bronchus and therefore dilating them (which in the asthmatic are constipated). There are rapid action (act immediately and its effect lasts between four and six hours) and prolonged action (acts between two and ten minutes after its administration and lasts between twelve and twenty-four hours depending on the compound). The main side effect is that they are cardiotonic, so they should be used with caution in people with heart problems. There are other anticolinergic bronchodilators, but they are used more in chronic obstructive bronchitis than in asthma.
- (b) Anti-inflammatory are mainly inhaled corticosteroids. They are very low doses of corticosteroids so they start to effect the third day of use and therefore should be used for a longer or longer time. They act by removing the inflammation of the bronchus (asmatics have swollen bronchus), are used in combination with bronchodilators and sometimes in both types of medications in a single inhaler, which is called mixed therapy.
- (c) Monoclonal antibodies They constitute a relatively recent treatment that has revolutionized the treatment of severe allergic asthma and chronic urticaria. It consists in the subcutaneous administration of omalizumab whose function is to block the union of the IgE to its receptor. It is always administered in the hospital.
- (d) Leucotriene inhibitors are a type of medication that acts on the receptors of leucotrienes (substance that actively participates in bronchial inflammation), which reduces bronchial inflammation. Its use is recommended for mild to moderate asthma that is not properly controlled. The main ones are montelukast and zafirlukast. Recent studies have shown their effectiveness in allergic rhinitis.
There are other types of anti-inflammatories such as disodium cromoglycate and nedocromil as well as oral corticosteroids.
For allergic rhinitis, antihistamines are basically used in tablets or inhaled via the nose or inhaled corticosteroids.
For urticarias, dermatitis and eczema, antihistamines or corticosteroids in different forms and combinations.
This is a brief review of symptomatic treatment and should never be used. replace the treatment given by your doctor.
Allergen Immunotherapy
The modification of the altered immune response is very useful in patients diagnosed with respiratory allergy (Rhinoconjunctivitis and Asthma), in which it is very difficult to avoid contact with the allergen, due to its ubiquity (pollens, mites, epithelia of animals or fungi) and in patients allergic to Hymenoptera venom.
In both cases it has been shown that the use of immunotherapy with allergens is capable of modifying the immunological alterations of allergic patients at different levels and improving symptoms consistently and for a long time. The use of this treatment must be carried out by specialized personnel and after a rigorous allergological diagnosis that identifies the agent causing the symptoms. It consists of the progressive controlled administration (subcutaneous or sublingual route) of a purified extract of the allergen responsible for the patient's symptoms, seeking that his body becomes accustomed or becomes "tolerant" to the allergen little by little.
There are several types of Immunotherapy or allergy vaccines, in general they are initially administered weekly or several days and once the maintenance dose is reached, it is done monthly (or weekly in America), usually requiring the vaccine to be do for 3-5 years, since its healing effect is slow and progressive. It is the only therapy capable of modifying the natural course of allergic diseases. In addition, as in all chronic diseases, the treatment of the allergic patient must include educational aspects, which include the characteristics of their disease, their therapeutic possibilities and the peculiarities of the allergen causing their symptoms. For this reason, a complete allergy study must be carried out in all patients suspected of having a disease of allergic origin, which must be the basis for all subsequent therapeutic decisions.
Prophylaxis
In allergies it is very important to take preventive measures (prophylaxis) of the allergen when it is avoidable.
In urban areas, allergens abound: smog, micromolds, pollens, mites (mites usually infest mattresses and, above all, carpets), pet hair can also carry allergens, for example, when a cat licks itself, it leaves his saliva in his hair, this saliva when dried flies in flakes through the air and can cause allergies in prone people. Cleaning, avoiding enclosed or very humid environments are prophylactic habits.
Specific vaccination against allergens in allergy sufferers may be helpful.
The seasonal change that goes from summer to autumn, with sudden cooling, increases the susceptibility to various noxes (including allergens), something similar, although to a lesser degree, occurs during the critical passage that occurs from winter to spring.
Breastfeeding
Several studies conclude that breastfeeding, compared with formula milk, may protect against the development of allergic diseases. However, other factors play an added role, such as genetics, exposure to allergens, smoking or lifestyle.
The presence of food allergens in human milk has been widely demonstrated, such as egg proteins, gluten (contained in wheat, barley, rye, oats, and all their hybrids), cow's milk and peanut. In general, concentrations are related to the amount of food eaten by the mother. Allergens pass rapidly into breast milk, within minutes after eating, and can remain for several hours.
This exposure to food allergens through breastfeeding has been suggested to induce tolerance in the infant, although how and when to expose infants to potential food allergens with the goal of inducing tolerance has not currently been established. tolerance or prevent the development of subsequent sensitizations.
In the case of gluten, neither early exposure to gluten nor duration of breastfeeding has currently been shown to prevent the risk of developing celiac disease, although delayed introduction of gluten is associated with delayed in the onset of the disease. This contradicts the recommendations issued in 2008 by the European Society for Pediatric Gastroenterology (ESPGHAN) for families of children at risk of developing celiac disease, which consisted of gradually introducing small amounts of gluten in the diet during the period between the first 4 to 7 months of life, while breastfeeding. Risk genetics (presence of the HLA-DQ2, HLA-DQ8 haplotypes or any of their alleles) it is an important factor that predicts the possibility of developing celiac disease.
Aerobiology and allergy
Aerobiology is the science of biological particles transported passively through the air, such as bacteria, fungal spores, very small insects, and pollen. One of the main fields of Aerobiology has been to analyze these particles to fight against the symptoms of pollinosis.
Spain has a Spanish Aerobiology Network (REA) [3], established in 1992 and whose coordinating center is located in the Department of Botany, Ecology and Physiology of the University of Córdoba. Among the tasks of this coordinating center are the dissemination of national pollen information in the different media. The Pan American Aerobiology Association (PAAA) [4] is a society of individuals who share a professional or academic interest in the science of Aerobiology.
The aerobiological method used and standardized by the Spanish Aerobiology Network is widely used in the scientific field. The data generated by the Spanish Aerobiology Network are subject to strict control, ensuring their air quality. Subsequently, the Minimum Recommendations of the aerobiological method, after an intense work of international consensus.
Aerobiology is a very useful tool for the fight against pollinosis. Some fields of Aerobiology deal with the study of airborne pollen, airborne fungal spores or the content of allergens in the environment, allergens. Other studies deal with prediction models of airborne pollen content or the study of the main sources of allergenic particles.
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