— Dr. Long Chelsea98.com Huizhou Education_Millions of Dragons of Great Health

Allergen testing refers to allergen testing for patients with allergic diseases to find the real cause of allergies, so as to carry out targeted prevention and treatment. Many allergic diseases are related to contact with allergens, including skin allergies, brain allergies, intestinal allergies and so on. Clinically, commonly used allergen testing methods include: skin testing and blood testing. Among them, skin tests, including prick tests, intradermal tests, and patch tests, are all performed directly on the skin; blood tests are blood tests to check the IgE antibodies and IgG antibodies in the blood to determine allergens.

1, Skin detection

(1) Point prick test and intradermal test

During operation, each sample to be tested is dropped on the skin, and then the skin under each sample needs to be punctured or injected into the skin. Therefore, when the needle punctures or penetrates the skin, you may feel a slight tingling sensation. If an allergic reaction occurs, there may be some itching, tenderness and swelling of the local skin, where the allergen solution is placed on the skin. After the test is complete, you can use a cold towel or hormone ointment such as hypoxamethasone cream to relieve itching and swelling.

(2) What factors will affect the results of the skin test?

It is difficult to find allergies accurately. If some details are not noticed, it will interfere with the test results even more. For example, taking antihistamines (such as loratadine, levocetirizine, fexofenadine, etc.) and tricyclic antidepressants (such as amitriptyline) will affect the results of skin test allergens. interference. Excessive sweating or partial showering in the patch test will cause changes in the concentration of the substance to be tested and will also interfere with the results.

(3) How to choose a suitable detection method?

Skin testing is a relatively easy and inexpensive method of testing. It is more reliable than blood testing in detecting inhaled (air) allergens such as pollen, dust, mold and pet dander. However, it is impossible to determine whether you are allergic to a certain food, and further tests (such as removing a certain ingredient in the diet or taking a certain food to observe whether the allergy occurs) are needed to further confirm the food allergen. Because it is more painful (21 needles are required, 40-60 needles are used in Europe and America), it is not suitable for children.

The blood test method is more expensive, but it can also be tested after oral antihistamines and tricyclic depression drugs, and is not affected by the drugs. It is suitable for patients who are very susceptible to skin allergies (the skin test may cause serious reactions) or patients who have skin diseases such as eczema (their skin diseases will affect the judgment of the results).

2, Patch test

Patch test is mainly used to check contact dermatitis. The specific method is to stick the reagent on the skin for observation for a period of time, and then judge whether you are allergic to this substance according to the skin's reaction to the contact material. Stick the small grid containing the sample to be tested on the back without tingling. However, if allergies occur, there may be severe itching. It is possible to remove the small box and notify the doctor. Test items include: drugs, rubber products, skin care products, preservatives, toys, home decoration materials, hair dyes, printed matter, textile dyes, bleaching agents, metal jewelry, spices and other industrial, agricultural and daily chemical products, including hundreds of categories Small class of allergens.

3, Cosmetic allergy testing

The allergens and allergic cosmetics can be accurately detected through closed patch method, light patch method, blister fluid detection method, scratch test method, etc., and guide patients to choose suitable cosmetics. By directly applying on the skin surface and receiving a certain dose of ultraviolet radiation at the appropriate wavelength at the same time, the detection of photosensitizers for phototoxicity and photoallergic dermatitis and the body's phototoxicity or photoallergic reaction to certain photosensitizers A skin test. When suffering from light allergic skin disease, in order to confirm the existence of light-sensitive substances, a light patch test should be done. Especially useful for external photosensitive materials.

4, IgEAntibodies and IgGAntibody detection

(1) IgEAntibody detection

IgE is also called reactin or cytophilic antibody. The content in normal human serum is very small, about 0.01~0.9mg/100ml, and the content is relatively stable, generally it can be measured by radioimmunoassay. Hypersensitivity diseases, such as exogenous asthma, hay fever, rhinitis, idiopathic dermatitis and other patients with serum IgE levels fluctuate greatly. For example, in patients with pollen allergies, serum IgE levels increase during the pollen season and decrease after the pollen season. IgE may be present in nasal fluid, bronchial secretions, breast milk and urine, and its content is similar to serum IgE. Parasitic diseases such as helminths, schistosomiasis and trichinella, infections of certain fungi (Candida albicans, Aspergillus, etc.) and certain Staphylococcus aureus infections can induce large amounts of IgE. Protozoan infection generally does not cause an increase in IgE content (but amoebic dysentery, especially amoebic liver abscess, can produce anti-amebic IgE antibodies). In certain liver diseases and myeloma, IgE levels are also abnormally elevated.

The production site of IgE is similar to SIgA. It is produced by the plasma cells in the respiratory tract (nasal, pharyngeal tonsils and bronchi) and the lamina propria of the digestive tract, and is distributed in the mucosal tissue, exocrine fluid and bloodstream of these parts. These sites are the entry portal for allergens and the prone sites for allergic reactions. IgE is a monomer with a molecular weight of 190kD. Its heavy chain has one more functional domain (CH4) than the γ chain, through which the domain binds to the cell. IgE has poor heat resistance and loses its binding ability within 4 hours at 56°C. Reductive alkylation with disulfide bonds can also make it lose its ability to bind to cells. IgE easily binds to skin tissues, mast cells, basophils in the blood, and vascular endothelial cells. This is related to the high content of cysteine and methionine in its disulfide bonds. In addition to the expression of IgE FcR on the above-mentioned cells, it can also be found on the surface of B cells, some T cells and macrophages, which may play an important role in regulating the production of IgE antibodies and defending against infection. Generally, FcεR on mast cells and basal granulocytes is called FcεRⅠtype, and those on B cells and T cells are called FcεRⅡtype.

IgE is the main antibody that causes type I hypersensitivity reactions, because its Fc segment is particularly easy to bind to the FcεR of basophils and mast cells. When antigens with more than two valence bind to IgE on cells, IgE molecules can be bridged. The presence of Ca2+ triggers the release of biologically active substances in cells. Whether IgE has a protective effect, there is no definite proof. Its anti-parasitic effects have long been reported. For example, IgE can make eosinophils migrate locally, and can mediate ADCC effects and kill worms.

(2) IgGAntibody detection

IgG is the main Ig produced by the secondary humoral immune response. It has the highest content in serum, reaching 600-1600mg/100ml, accounting for 75%-80% of the total serum Ig. There are great differences between different individuals. IgG is mostly monomers with a molecular weight of 150kD, and a small amount of IgG also exists in the form of multimers. IgG is mainly synthesized by plasma cells in the spleen and lymph nodes, with a half-life of about 23 days. Therefore, when using G-ball for treatment, it is advisable to inject once every 2 to 3 weeks. IgG plays an important role in the body's defense mechanism because of its high content and wide distribution. Compared with other Ig, it is easier to diffuse into the interstitial space through the capillary wall, playing an anti-infection, neutralizing toxin and conditioning role. IgG occupies about 50% in plasma and tissue fluid, so almost any tissue and body fluid of the body, including cerebrospinal fluid, have IgG distribution. IgG is the only Ig that can pass through the placenta, so it plays an important role in anti-infection of newborns. The IgG content in the placenta is much higher than that in the serum.

The Fc segment of IgG can bind to Fc receptors on the surface of neutrophils, monocytes, macrophages, K cells, etc., thereby exerting its opsonizing effect and activating K cells to kill target cells. The Fc segment of certain subclasses of IgG can be fixed to the skin, causing type I hypersensitivity, and can also bind to the protein A (SPA) on the staphylococcal cell wall.

Gamma spheres used for treatment mainly contain IgG. IgG extracted from normal human serum can have a variety of antibody activities, such as anti-hepatitis A, hepatitis B, measles, mumps virus, tetanus and diphtheria antitoxin. In other words, most of the antibacterial and antiviral antibodies belong to the IgG type antibody. In addition, some autoantibodies, such as anti-nuclear antibodies in patients with systemic lupus erythematosus, anti-thyroglobulin antibodies, antibodies that cause type II and III hypersensitivity reactions, and blocking antibodies (promoting tumor growth) are mostly IgG.

(3)IgEAntibodies andIgGThe difference in antibody detection

IgE antibodies and IgG antibodies are two common media used to detect allergens, but the specific allergies they target are different:

IgE antibody test: test nickname: "acute allergen test"; "immediate allergy test";

Test items: 80 most common allergens (20 inhaled allergens and 60 food allergens).

20Kinds of inhalation allergens:

  • Microorganisms (moulds): Penicillium, Cladosporium, Fumigatus, Candida albicans, Alternaria;
  • Pollen: bermudagrass, pasture, hogweed, wormwood, asteraceae plants;
  • Mites: house dust mites, dust mites, and non-clawed mites;
  • Drift cockroaches: cat dander, dog dander, chicken dander, duck dander, German cockroach, Asian cockroach;
  • Other: latex.

60Food allergen

  • Cereals: wheat, oats, corn, rice, buckwheat, malt;
  • Vegetables: tomato, carrot, potato, celery, melon, mushroom, spinach, cabbage, pumpkin, cucumber, cabbage (broccoli), ginger, yam, taro;
  • Seafood: salmon, cod, crab, shrimp, peacock clam, tuna, lobster, oyster (oyster);
  • Fruits: kiwi (kiwi), orange, coconut, strawberry, apple, lemon, pineapple, cherry, grape, papaya, watermelon, cranberry;
  • Nuts: peanuts, soybeans, almonds, sesame seeds, cocoa beans, cashews, vanilla beans;
  • Dairy products: milk, goat milk, cheese, egg white, egg yolk;
  • Meat: pork, beef, chicken, lamb;
  • Spices: garlic, mustard;
  • Other: Yeast.

Adapt to the crowd: Everyone is suitable for this test, especially the following people:

  • People who have eczema, skin allergies, nasal allergies, asthma, food allergies, etc., but cannot find the cause.
  • People with allergies or allergic diseases.
  • Both parents or one of them are allergic.
  • School-age children (because their immune system is not yet sound, they are susceptible to allergens).
  • Focus on personal health managers.

Detection method:

  • A small amount of blood will be drawn by someone for inspection.
  • The report will be issued after about 14 days, with recommendations to avoid or eliminate allergens.
  • There is no need to fast before blood draw.

Necessary for testing:

  • Allergies can range from itchy skin to severe complications that can be fatal. The most severe case of food allergy died within 5-8 minutes.
  • Without a professional allergen test, it is generally difficult to determine the allergen on its own. Previously, some parents mistakenly believed that the child’s eczema was caused by seafood, but after diagnosis, it was discovered that the child was allergic to milk; some people with nasal allergies thought that they were allergic to dust mites, and finally discovered that the allergen was cat hair at home . Therefore, if you want to truly get out of the clutches of allergies, you must first find your allergen, so that you can prescribe the right medicine.

IgG antibody test: test nicknames: "chronic food allergy test"; "food intolerance test"; "fit food test"; test items: the following categories are more than 200 kinds of foods that most commonly cause intolerance: food types : Cereals, beans, dairy products, eggs, meat, fish, seafood, vegetables, fruits, nuts, spices, beverages, and others.

Adapt to the crowd:

  • People who often experience constant weight gain, fatigue, brain fog (difficulty in maintaining clear mind and concentration), headache, acne, eczema, diarrhea, abdominal distension, constipation, etc., but the cause cannot be found.
  • People with allergies or allergic diseases.
  • Both parents or one of them are allergic.
  • School-age children (because their immune system is not yet sound, they are susceptible to allergens).
  • Pregnant mothers (pregnancy is the golden period to reduce the birth rate of allergic babies) and breastfeeding women (improper diet of mothers may cause baby allergies).
  • Focus on personal health managers.

Detection method:

  • Since sampling is relatively simple, you can also choose to sample at home and send the sample to the laboratory after collection.
  • The report will be issued after about 14 days, with corresponding dietary recommendations and precautions.
  • There is no need to fast before blood draw.

Testing advantages:

  • IgG testing is the best method for detecting food intolerance reactions (has been ISO quality certified).
  • It only needs to be tested once in a lifetime, which can accurately measure the human body’s permanent intolerance to food.
  • Traditional testing methods such as cytotoxicity testing and enzyme-linked immunosorbent assay cannot detect specific foods that cause intolerance, while IgG testing can accurately distinguish which foods have temporary or long-term intolerance to the body. Help the tester more effectively eliminate related discomfort.
  • The results can be accurately predicted without going through the diet control period.
  • Sampling can be done by itself without doctor's assistance, and the operation is simpler and more convenient.

Final words

Serum testing methods are mostly used to detect immediate allergic skin diseases, such as urticaria, atopic dermatitis, etc., with high accuracy and relatively convenient operation. But the disadvantage is that the sensitivity is not enough, and some non-IgE-mediated allergies cannot be detected. The skin prick test has the advantages of low risk, high sensitivity, simple operation, simple equipment, short detection time, and can measure multiple allergens in one test. It has good correlation with clinical allergic diseases. But the disadvantage is that the specificity is not enough, and it is difficult for young children to cooperate. A very small number of people, especially infants under 2 years of age, need to prevent serious allergic reactions. Patches are used for the diagnosis of allergens in patients with contact dermatitis, especially cosmetic dermatitis. It is used more by adults and less by children. High accuracy, no trauma, simple operation. The disadvantage is that the observation result takes a long time, and some people may cause severe local allergic reactions. Therefore, it is not recommended for infants and young children. Intradermal test (skin test) is a special method for detecting allergens, which is used to detect immediate drug allergic reactions. Because it is invasive and has certain risks, it needs to be monitored in the hospital. Therefore, it is rarely used to detect allergens except for drug skin tests in clinical practice.

Irregular test results will lead to a large number of false results. Many children who are not allergic to dairy products, poultry eggs, fish and shrimps will be labeled as allergic, and have to "farewell" to these foods from now on. Conducive to the growth and development of children, it will also bring additional psychological burden, and its more serious side effects may even be fatal. Most allergic patients cannot detect allergens. There are more than 20,000 kinds of allergens in nature, but only 500 to 600 kinds of allergens can be detected at present, and only about 20% of them can be found clinically. . In other words, 80% of patients spend hundreds of yuan to do allergen testing, which is in vain.

So, how should we detect or treat various allergies? Please continue to follow this series.

*** Every article has been carefully written, edited and checked by Huizhou experts. Please trust the experts’ opinions and suggestions.If you have any questions, please email info@chelsea98.com ***

Chelsea98.com--Wise Week Million Dragon's Great Health Project Dr. Kyle Long, registered dietitian, registered health manager, from Smart Week Smart Financial Education Group-Sincere, clear and efficient personalized FAH financial quotient and health quotient education

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