The real cause of the allergy, and therefore the targeted prevention and treatment, resulting in repeated aggravation of the disease and persistent treatment. Therefore, it is recommended that patients with frequent allergies must undergo allergen screening tests to find out whether contact, ingestion or inhalation allergens are causing the allergic reaction in order to solve the problem at its root. Never treat allergies as a minor problem and ignore the examination and treatment, which eventually leads to serious consequences. Normative examination methods: 1. Skin prick test Usually, a dip of various common allergens is applied to the flexor side of the forearm at a certain distance, and then the epidermis is gently punctured with a special prick needle, allowing the allergens to come into contact with the immune cells in the skin, inducing a local erythema reaction. Pros: Less painful, more sensitive, easier to perform, results usually seen in 20 minutes. Disadvantages: If you have taken antihistamines or hormones, it may affect the test results, and there is also a certain amount of false positives. 2.Intradermal test Similar to penicillin skin test, but usually performed on the outside of the upper arm. The principle is the same as the skin prick test, but the positive rate is higher than that of the prick test. 3, peripheral blood specific IgE test 3-5ml of venous blood can be taken for examination. This method is not affected by drugs, sensitivity and specificity are higher. 4, skin patch test Usually on both sides of the upper back spine in a certain order and interval patch common allergens, 48 hours later to observe whether there is local erythema papular blistering and other reactions. This method is suitable for delayed hypersensitivity reactions, such as various contact dermatitis. 5, excitation test A certain concentration of allergen can be introduced into the body through the eyes, nose or orally to induce an allergic reaction, so as to determine or exclude the allergen. This method is the gold standard for detecting allergens, especially food and drug allergens, but there is a risk of causing serious allergic reactions, and it needs to be used with caution under the supervision of a professional physician.