allergy



Overview.

What is a Metamorphic Reaction?

Definition

Metamorphosis is a specific immune response that causes tissue damage or physiological dysfunction when the body is re-stimulated by the same antigen.

The immune system mistakenly treats substances (e.g., food, pollen, drugs, etc.) that are supposed to be necessary or harmless to the body as harmful foreign substances, causing tissue damage or physiological dysfunction.

Diseases caused by allergic reactions are allergic diseases.

Typing

According to the typing principle proposed by Coombs and Gell in 1963, allergic reactions are categorized into four types according to the immune mechanism, reaction time and other characteristics. There are also 2 special types in type II as type V and type VI allergic reactions, thus divided into six types.

Also known as rapid-onset hypersensitivity reactions, the most common. Common diseases include allergic skin diseases (e.g. acute urticaria), allergic rhinitis (allergic rhinitis), allergic asthma (allergic asthma), allergic conjunctivitis (allergic conjunctivitis) and anaphylaxis.

Also known as cytotoxic or cytolytic hypersensitivity, common disorders include hemolysis of the newborn, autoimmune hemolytic anemia, and transfusion reactions with incompatible blood groups.

Also known as immune-complex hypersensitivity reactions, common diseases include eosinophilic granulomatous vasculitis, systemic lupus erythematosus and immune-complex glomerulonephritis.

Also known as delayed-type hypersensitivity, it is more common, and common diseases include contact dermatitis and transplant rejection.

Also known as cell-stimulating type. It is characterized by the combination of a certain antibody against cellular components with antigen on the cell membrane, which does not activate the complement and does not destroy the cell, but acts as a stimulus to enhance cellular metabolism and increase secretion.

This type is originally a special type of type II allergic reaction.

It is also known as antibody-dependent cytotoxicity, which is characterized by non-phagocytic killing of target cells.

It belongs to the category of type II allergic reactions.

Morbidity

In recent years, the incidence of allergic diseases in China has increased significantly, and it has become a common health problem faced by the nation and deserves the attention of the whole society.

Data from epidemiological surveys conducted by the World Allergy Organization (WAO) on allergic diseases in 30 countries/regions show that 22% of the population suffers from allergic diseases, such as allergic rhinitis, asthma, conjunctivitis, contact dermatitis, food allergy and so on.

Questions you may be concerned about

What are the diseases that can be seen in an allergist?

The Department of Allergy deals with a number of allergic diseases.

The term “allergic reaction” refers to an abnormal immune response of the body. People with allergies overreact to certain substances and an allergic reaction occurs when they come into contact with these substances (i.e. allergens, or sensitizers) again.

Common diseases include: allergic asthma, allergic rhinitis, anaphylaxis, food allergy, drug allergy, hives, etc.

Should I see an ENT or an allergist for allergic rhinitis?

Allergic rhinitis can be effectively diagnosed and treated in both ENT and Allergology.

Allergic rhinitis, also known as “allergic rhinitis”, is an allergic disease that occurs in the mucous membrane of the nose, with the main symptoms being nasal congestion, runny nose and sneezing. Allergic rhinitis can be treated either in the ENT department or in the allergy department. For hospitals that do not have an allergy department, you can choose the ENT department.

What kind of allergic reaction is penicillin allergy?

Penicillin allergy mainly causes a type I allergic reaction.

The pathogenesis of penicillin allergy involves 4 types of allergic reactions, of which the main one is type I (rapid-onset hypersensitivity), which is related to the specific IgE of penicillin degradation products. Severe systemic reactions such as urticaria, hypotension, angioedema and anaphylaxis can be triggered.

Skin test before the use of penicillin in the clinic can effectively determine whether the penicillin is allergic to penicillin, to avoid the occurrence of serious allergic reactions.

Causes

Causes

Allergic reactions are the result of a combination of genetic and environmental factors. People with allergies are sensitized to certain substances, and when they come into contact with these substances (i.e. allergens, or allergens) again, an allergic reaction will occur.

Genetic factors

There is a clear genetic predisposition to allergic reactions. For example, if an immediate family member has an allergic disease, the likelihood of an abnormal immune function is high, and there is a high likelihood that an allergic reaction will occur as a result of the allergen. However, heredity is only a foundation, and the ability to induce an allergic reaction at a later stage is very much related to the growing environment.

Environmental factors

In recent years, as industrialization, urbanization and globalization continue to accelerate, there are more and more types of food and processing techniques, and the use of a variety of chemical additives in food and toiletries makes the relevant population more susceptible to allergies.

Populations growing up in less hygienic conditions, especially in environments with a high prevalence of infectious diseases, have a lower incidence of anaphylaxis, while areas with better sanitation and hygiene have a higher incidence of anaphylaxis.

Based on historical data, it appears that the large spread of sanitation and clean water has been accompanied by a rapid increase in the incidence of allergic diseases, leading to the development of the hygiene hypothesis, which needs to be further substantiated.

Allergens

Foods: e.g. milk, egg whites, wheat, peanuts, soybeans, nuts, fish, shrimp, crab and shellfish.

Inhalants: e.g. pollen, dust mites, fungi, animal dander, etc.

Insect toxins: e.g. insect bites such as bees, houfen, etc.

Drugs: such as penicillin, sulfonamides and other antibiotics, procaine, rocuronium bromide, propofol and other anesthetic drugs.

Allogeneic blood products: e.g. allogeneic plasma, tetanus vaccine, rabies vaccine, etc.

Pathogenesis

The development of any kind of allergic reaction requires three stages.

The first stage

Called sensitization phase. This is the preparatory stage of an allergic reaction. In this stage, when allergic people are first exposed to a sensitizing substance (i.e. allergen), the body produces a kind of antibody, called specific antibody, and the lymphocytes in the body are also sensitized.

The second stage

The second stage is called the exposure stage. In this phase, the affected person comes into contact with the sensitized allergen again through ingestion, inhalation, injection, skin application, etc., thus inducing a subsequent reaction.

Third stage

Called the seizure phase. Specific antibodies in the body rapidly bind to these allergens, causing the corresponding effector cells to release various chemical mediators or cytokines, which further mediate a series of reactions in various tissues and organs, manifesting various allergic symptoms.

Symptoms

Symptoms of allergic reactions are varied, ranging in severity from mild to severe, depending on the site of occurrence and allergens.

Systemic allergic reactions

Also known as “severe allergic reaction”, anaphylactic shock may occur in severe cases. Common allergens are drugs, food and insect venom.

The onset of the reaction is usually rapid after exposure to the allergen, but a delayed reaction may also occur.

The main manifestations are extensive itching, urticaria, and angioedema.

It may be accompanied by multi-system symptoms, such as laryngeal edema, airway spasm, nausea, vomiting, abdominal pain, diarrhea, palpitations, dizziness, etc., and may be accompanied by blackout and syncope due to hypotensive shock.

Localized allergic reactions

Common allergic diseases occurring in various parts of the body include the following.

Allergic skin diseases

The affected parts are skin and appendages, such as atopic dermatitis, contact dermatitis, acute urticaria, angioedema and so on.

The main manifestations are itchy skin, polymorphic lesions, and may have a tendency to ooze.

Allergic keratitis/conjunctivitis

The affected areas are cornea and conjunctiva.

The main symptoms of conjunctival involvement are itching, burning sensation, conjunctival congestion, tearing, and increased secretion.

Involvement of the cornea may also include photophobia, decreased visual acuity, and even blindness due to corneal perforation.

Allergic rhinitis

The affected part is the nose, and the typical symptoms are nasal itching, paroxysmal sneezing, large amount of watery nasal discharge, nasal congestion and loss of smell.

Nasal itch: it is a special sensation that occurs locally after the sensory nerve endings of the nasal mucosa are stimulated. Itchy eyes can be aggravated by the presence of nose-eye reflex.

Sneezing: a reflex action. It is a paroxysmal attack, ranging from a few, a dozen or dozens.

Nasal discharge: a large amount of clear watery nasal discharge, which is a characteristic manifestation of hypersecretion of nasal mucosa.

Nasal congestion: varying degrees of severity.

Olfactory loss: partly associated with nasal mucosal edema.

Allergic asthma

The affected area is the lower respiratory tract and is closely related to rhinitis.

Typical symptoms are recurrent cough, chest tightness, breathlessness, wheezing, dyspnea, etc., often worse at night.

Allergic digestive diseases

The affected area is the digestive tract, such as eosinophilic esophagitis, food protein-induced small bowel colitis syndrome, celiac disease, etc..

The main manifestations are repeated episodes of acid reflux, heartburn, nausea, vomiting, abdominal distension, abdominal pain, diarrhea, etc. after eating.

Consultation

Department of Medicine

Department of Allergic Reactions

Repeated itchy eyes, itchy nose, sneezing, runny nose, nasal congestion, coughing, wheezing, itchy skin, rash, abdominal pain, diarrhea, etc., should be alerted to anaphylaxis, and timely consultation is recommended.

Emergency Department

If you suddenly develop severe symptoms such as a generalized rash, shortness of breath, wheezing, and impaired consciousness after eating a certain food, injecting or taking a certain drug, or coming into contact with a certain substance, it is recommended that you go to the Emergency Department as soon as possible or call the 120 emergency number.

Preparation for medical treatment

Preparing for a visit: registering, preparing information, and common problems

Tips for seeking medical treatment

When you have symptoms, record what you have eaten or been exposed to that day, and the duration of the symptoms for the doctor’s reference when making a diagnosis.

Preparation Checklist

Pay particular attention to the time of onset of symptoms, special manifestations, etc.

Are there any triggering factors for the symptoms? What have you eaten or been exposed to before the onset of symptoms?

How many times did the symptoms occur and how long did they last?

What other symptoms are associated with the rash?

Has there been any severe respiratory distress, impaired consciousness, etc.?

Has anyone in the family had similar symptoms or suffered from allergic diseases?

Is there any history of food or drug allergy?

Is there a clear history of allergen exposure?

Test results in the last six months, which can be brought to the doctor’s office

Skin tests: skin prick test, intradermal test, patch test

Laboratory tests: specific IgE antibody test, anti-hematocrit antibody test, immune complex test

Medication use in the last 3 months, if available in box or package, bring with you to the doctor’s office

Antihistamines: Diphenhydramine, Chlorpheniramine, Loratadine, Cetirizine, Ebastine

Others: montelukast sodium, glucocorticoids, sodium cromoglycate, ketotifen

Diagnosis

Disease Diagnosis

The doctor’s diagnosis of allergic reactions relies on a detailed history, clinical manifestations, and a combination of skin tests and laboratory tests to confirm the diagnosis.

Medical history

There is a clear history of allergen exposure.

Symptom onset is related to season, diet, medication and environmental triggers.

Treatment for allergic reactions has been effective.

Immediate family members have had similar symptoms or suffered from allergic diseases.

Clinical manifestations

Symptoms of an allergic reaction following exposure to an allergen, which may involve multiple organ systems throughout the body.

Skin test

Abbreviated as skin test, it mainly includes skin prick test, intradermal test, patch test.

It is a method of testing for Type I allergic reactions by applying a small amount of highly purified allergen liquid to the patient’s forearm, and then gently puncturing the surface of the skin with a puncture needle.

The presence of a visible localized skin tangle is considered positive, indicating sensitization to the allergen, which is important for disease analysis and treatment.

The intradermal test is a test for type I allergic reactions in which a small amount of highly purified allergen extract is injected into the skin of the outer side of the upper arm, producing a dermatomal mound 1 to 2 mm in diameter. In general, the intradermal test is more sensitive and the skin prick test has better specificity.

It is mainly used to detect type IV cutaneous allergic reactions and helps to determine the relationship between the suspected sensitizer and the disease as well as to further search for allergens.

Localized skin changes such as erythema, infiltration, papules and blisters are considered positive.

Laboratory Tests

Immunoglobulin E (IgE) is the antibody that mediates type I allergic reaction, so the detection of serum allergen-specific IgE is valuable for the diagnosis of type I allergic reaction and the determination of allergens.

Rh antibody test: In neonatal hemolysis due to Rh blood group incompatibility, the Rh antibody test is positive if the mother is Rh-negative but has produced anti-Rh antibodies in her body.

Anti-human globulin tests: These include the direct Coombs test and the indirect Coombs test, which can assist in the diagnosis of immune-related hemolysis.

Immune complexes exist in the body in two ways, circulating immune complexes present in the blood and immobilized immune complexes in tissues.

Circulating immune complexes are detected by physical, complement, anti-Ig, and cellular methods.

The method of detection of immobilized immune complexes in tissues is immunohistochemical technique. Firstly, a tissue specimen is taken from the appropriate pathological site for frozen section, stained with fluorescently labeled anti-human IgG or anti-human C3, and a positive reaction is seen when the corresponding site shows fluorescence under a fluorescence microscope.

Differential diagnosis

Allergic diseases involve complex mechanisms, and there are a variety of diseases that require differential diagnosis depending on the site or system involved, but in general, it is important to differentiate them from non-allergic inflammatory diseases of the affected system.

Treatment

Identification and avoidance of allergens

Identifying and avoiding exposure to allergens is the most basic and important treatment.

Identification of allergens

Your doctor will take a medical history, skin tests, and blood tests to find the allergen and plan the next step in your treatment.

Avoiding or minimizing exposure to allergens

If the allergen is a food, drug, chemical, or metal, avoid exposure to that allergen as much as possible.

If the allergen is an inhalant allergen, such as dust mites, fungi, pollen, etc., which is difficult to avoid completely, you should try to minimize the exposure to the allergen, such as preventing dust mites and removing molds at home, and wearing masks when you go out during pollen season.

Symptomatic treatment with medication

The aim is to relieve the symptoms. Commonly used drugs include antihistamines, glucocorticoids, leukotriene receptor antagonists, mast cell membrane stabilizers, adrenaline, immunosuppressants, etc. The usage, dosage, and course of treatment should be in strict accordance with medical advice.

The common people commonly known as “anti-allergy drugs”, can competitively bind the histamine H1 receptor, inhibit the role of the important mediator in the metamorphosis reaction – histamine, so that you can alleviate the itching of the skin, air masses, runny and other symptoms.

Because the first generation of antihistamines (such as phenylephrine, chlorpheniramine, etc.) has a more obvious central sedative effect, so the second generation of antihistamines is commonly used in the clinic, such as loratadine, cetirizine, ebastine, etc.

Glucocorticoid

Glucocorticosteroids have a strong anti-inflammatory effect, and are often used selectively according to the site of disease involvement.

Topical glucocorticosteroids are preferred and safe, such as topical skin hormones, nasal spray hormones, inhaled hormones, etc. If the disease is more severe and more systems are involved, oral, intramuscular or intravenous administration may be considered.

Leukotriene receptor antagonists

Can block another important class of mediators, leukotrienes, that cause allergic inflammation; commonly used drug is montelukast sodium.

Mast cell membrane stabilizer

Commonly used drugs, such as sodium colgate and ketotifen, can reduce mast cell degranulation and lower the level of inflammatory mediators, thus improving symptoms.

Epinephrine

It is the first choice emergency drug for severe allergic reactions. Patients with this disease should carry it with them and inject it intramuscularly if necessary.

Immunosuppressants

Indicated in allergic dermatoses to improve pruritus.

Desensitization therapy

Drug desensitization therapy

If the patient is allergic to a certain drug (e.g. sulfonamides, insulin, etc.), but must be used because of the condition, under the close supervision of the physician, the drug desensitization treatment can be carried out by using a small dose of the drug, short intervals (20-30 minutes) multiple administration, but the effect is temporary, and the reactivity will be restored again after a period of time after stopping the use of the drug.

Specific allergen immunotherapy

For inhaled allergens (e.g. pollen, dust mites, fungi, etc.), medication can be given by subcutaneous injection or sublingual administration, from low to high doses, so as to make the body tolerant to the allergens, but it is necessary to adhere to the treatment for more than 3 years.

Chinese medicine treatment

Some Chinese herbal formulas and proprietary Chinese medicines have also shown some clinical efficacy in allergic diseases and are worthy of further study.

Prognosis

Cure

Allergic diseases are not easy to be cured, and once specific antibodies are formed, they are difficult to disappear. The disease usually recurs and may progress to multi-organ involvement, and severe reactions may even be life-threatening. Therefore, patients should follow the requirements of allergy specialists to take regular medication in sufficient quantity and duration, and have regular outpatient follow-ups.

Hazards

Allergic diseases often start at a young age, and adolescents are prone to them. The chronic and prolonged course of the disease can cause damage to multiple organs and systems, and in severe cases, fatal reactions can occur.

In addition to the physical effects of the disease, it also has a great impact on the patient’s psychology, socialization, work, study, and even the quality of life of the whole family.

Daily

Reasonable diet

Eat a light diet, avoid alcohol, spicy and other stimulating foods.

Allergic people should be cautious of eating photosensitive foods, such as mud snail, ashwagandha, zinnia, snow pea, lettuce, fennel, amaranth, caper, celery, turnip leaves, spinach, buckwheat, parsley, safflower grass, greens, mustard greens, figs, oranges, lemons, mango, pineapple and so on.

Do not overly fast, especially for growing children, should be under the guidance of specialists to achieve a balanced diet, to ensure that the body’s nutritional intake.

Avoid foods that are known to cause sensitization. Foods that are clearly non-allergenic should be consumed routinely and diversely.

Regular review of allergens at the allergy clinic should be conducted to guide dietary intake and avoid malnutrition.

For exclusively breastfed children, it is still recommended to continue breastfeeding; at the same time, the mother should avoid eating the allergens of the child. For example, if the infant is allergic to cow’s milk protein, the mother should avoid cow’s milk and its products, and take vitamin D and calcium supplements.

If the child is allergic to formula, alternative formulas (e.g., deeply hydrolyzed and amino acid formulas, or soy milk powder) can be chosen under medical supervision.

Complementary foods: After avoiding all foods and their products that have clearly triggered allergy, a single variety can be introduced in the normal sequence of complementary foods, and each food should be observed continuously for 1 week after its introduction.

Skin care

For those with atopic dermatitis, eczema, etc., attention should be paid to the daily use of cotton clothing, moisturizing, sun protection, and avoiding contact with irritating toiletries.

Psychological balance

Pay attention to mental health, release pressure in time, avoid anxiety, depression, excessive tension and other bad emotions.

Improve the environment

For indoor allergens, take precautions against dust mites and mold, and avoid contact with animal saliva, dander and excreta.

For outdoor allergens, wear masks and goggles when going out during the season that triggers allergic reactions, and pay attention to indoor air purification and humidification.

Medical information

If you have had a severe allergic reaction, you should carry a medical identification card with you or inform others of the allergen in advance.

Those who have a history of drug allergy should avoid reapplying such drugs and inform the doctor when seeking medical treatment.

Learning about the science

Since anaphylaxis is often a chronic disease, effective treatment requires a high degree of cooperation from the patient. Therefore, patients and their families should learn and understand the scientific knowledge of the disease, especially for anaphylaxis, they should be familiar with the use of rescue medications, and it is recommended that they consult with their doctors to recommend reliable sources of scientific information.

Prevention

The most important aspect of prevention is to avoid triggers, i.e., to avoid exposure to allergens.

Improvement of environment

Regular cleaning of the environment, avoiding domestic pets, reducing dust mites, pollen, animal fur and other allergens in the environment.

Adjust diet

Avoid foods that are likely to cause allergic reactions. Common allergens are eggs, milk, peanuts and other leguminous plants, nuts and so on.

Allergic people should be cautious of eating photosensitive foods, such as mud snail, ashwagandha, zinnia, snow pea, lettuce, fennel, amaranth, caper, celery, turnip leaves, spinach, buckwheat, parsley, safflower grass, greens, mustard greens, figs, oranges, lemons, mango, pineapple and so on.

For foods that you are clearly not allergic to, you can eat them routinely and diversely to achieve a balanced diet.

Daily Protection

Wear a mask when you go out during the allergy-prone season, and avoid going to parks or forests where there are a lot of allergens.

If you have had an allergic reaction before, you should carry a medical identification card with you or inform others in advance.

Pay attention to medication

People with a history of drug allergy should avoid reapplying such drugs and inform their doctors when seeking medical treatment.