The term 'allergy' is not new to everyone. For example, allergic dermatitis, allergic rhinitis, allergic asthma... all have deep involvement in allergic reactions. About 30% - 40% of the world's people are troubled by allergies, while there are more than 200 million people with allergies in China!

　　So, what exactly is allergy?

　　Allergy is an 'allergic reaction' of the body and an abnormal reaction to normal substances (allergens). Under normal circumstances, when foreign substances enter the human body, they are mostly faced with two fates:

　　①If recognized as useful or harmless substances by the body, these substances will live in harmony with the human body and eventually be absorbed, utilized or naturally discharged.

　　②If these substances are identified as harmful substances, the immune system of the body will immediately react to expel or eliminate them.

　　This is the protective effect of immune response, but if this response exceeds the normal range, that is, when the immune system attacks harmless substances, this situation is called“Allergy”。

　　Allergy can be divided into four types clinically:

　　[Type I], also known as immediate anaphylaxis, is caused by a specific type of antigen, which is what we call an allergen.

　　[Type II] Pathological immune reaction mainly causing cell lysis or tissue damage, such as transfusion reaction with inconsistent blood type, hemolytic reaction of newborn, etc.

　　[Type III] It is also called immune complex type hypersensitivity reaction or vasculitis type hypersensitivity reaction, which causes tissue inflammation damage, such as partial glomerulonephritis.

　　[Type IV] It is also known as delayed anaphylaxis, which is mediated by T cells and is characterized by pathological damage mainly caused by infiltration of monocytes and lymphocytes.

　　Allergy is the main representative of type I allergy, which can be roughly divided into allergic reaction and allergic disease in clinic.

　　Allergic reaction is a systemic syndrome in which the body reacts abnormally to allergens;

　　Allergic disease refers to the occurrence of certain diseases caused by allergy involving certain organs and tissues, such as allergic asthma, allergic rhinitis, and certain skin diseases.

　　[Mechanism and process of anaphylaxis]

　　Allergens are the antigenic substances that cause body allergy. There are 2000-3000 common allergens:

　　1、Inhalation allergens: such as pollen, dust, animal fur, lampblack, etc;

　　2、Ingestion allergens: such as milk, eggs, seafood, alcohol, oral drugs, etc;

　　3、Contact allergens: such as hot and cold air, ultraviolet light, metal ornaments, cosmetics, plant leaves, etc;

　　4、Injectable allergens: such as penicillin, vaccine, xenogeneic serum, etc.

　　There are five types of antibodies in human body: IgG, IgM, IgA, IgD and IgE. The antibody related to allergic reaction is IgE, which is the lowest antibody in human serum. However, the content of IgE in allergic patients will increase significantly, and IgE is the only clinical indicator for diagnosis of allergy. IgE is mainly synthesized by B cells in the lymphoid tissue of the mucous lamina propria of the nasopharynx, tonsils, trachea and gastrointestinal tract, which are also the places where allergens are easy to invade and trigger allergic reactions.

　　It is generally believed that people have allergies because of two factors. On the one hand, it is a genetic factor, which is caused by the parents' genes. If one of the parents has an allergic disease, the probability of children suffering from allergic disease will increase by 30% to 40%; If both parents have allergic diseases, the probability of children suffering from allergic diseases will increase by 60% or 70%.

　　In addition to genetic factors, another important factor is [environment]. That is to say, although a child inherits the allergic quality of his parents, if there is no allergic environment, he may not suffer from allergic diseases for life.

　　How to treat allergy?

　　The most effective way to treat stubborn allergy is to find out the allergen. In its guidance document on immune desensitization therapy, the World Health Organization (WHO) clearly pointed out that immune desensitization therapy is the only fundamental treatment for allergic diseases. The so-called desensitization treatment is to make certain allergens into preparations with different concentrations, and repeatedly inject them into patients with positive skin test of corresponding allergens. The dose is from small to large, and the concentration is from low to high, and gradually induce patients to tolerate the allergen without allergic reaction. This process generally takes 3-5 years.

　　Be Careful：

　　◆Desensitization therapy is usually applied to patients with a single or small number of allergens. At present, only the patients with dust mite allergy can receive desensitization therapy in China;

　　◆Children under 5 years of age and pregnant women are not suitable for this treatment;

　　◆Even if the conditions are met, desensitization therapy will still be ineffective for some patients.

　　In addition, drug treatment is commonly used, such as oral antihistamines, or local use of hormones, which can alleviate symptoms to a certain extent. However, antiallergic drugs have certain side effects and are not recommended for long-term use.