Allergic diseases are a group of diseases that result from a protective or harmful immune response of the body to specific exogenous proteins. The common diseases include anaphylaxis, urticaria, angioneurotic edema, allergic rhinitis, bronchial asthma, hemolytic anemia, thrombocytopenic purpura, vasculitis, serum sickness, eczema, eruptive drug rash, and exfoliative dermatitis. Every person may suffer from these diseases for a short time or for a long time during his or her lifetime. If we can understand the mechanisms, clinical manifestations, treatment methods and the confusion and helplessness of current medicine in these diseases, we will be able to face them correctly, and the doctors and patients will be able to achieve better treatment results. From today, I will answer the questions from patients and the knowledge I have. 1.What is allergic disease? Allergic diseases are diseases caused by the immune system reacting to non-toxic antigens. (Immunobiology by Charles A, Janeway et al. Qian F, Ma Rui, eds). It is a protective or harmful immune response of the body to a specific exogenous protein, and the medical term for this immune response is metamorphic reaction. The term allergy is based on the combination of the Greek words allos (changed) and ergos (reaction). There are several types of allergic reactions: Type I: tachyphylaxis (e.g., anaphylaxis, urticaria, angioneurotic edema, allergic rhinitis, bronchial asthma, etc.); Type II: cytotoxic/cytolytic (e.g., hemolytic anemia, thrombocytopenic purpura, etc.); Type III: immune complex (e.g., vasculitis, serum sickness, etc.); Type IV: delayed or cell-mediated (e.g., eczema, eruptive drug rash, exfoliative dermatitis, etc.). exfoliative dermatitis, etc.). The first 3 types are mediated by antibodies, while type IV is mediated by cytokines.