The condition of skin allergy varies from person to person, and patients should seek medical attention promptly to determine the examination method after a comprehensive diagnosis by a doctor. 1. Blood test: By detecting specific IgE (immunoglobulin E) in the blood, the patient can determine whether there is an allergic reaction, and the patient does not need to be fasting. The common allergenic foods include milk, egg white and beef with high protein content, as well as seafood, such as crab, shrimp, sea fish, etc.; allergenic inhalants are commonly poplar wool, dust and animal hair, etc.; 2. If the patient is allergic to the allergen, red and swollen patches similar to mosquito bites will appear at the puncture site, accompanied by itching or skin color change; skin test is to inject a small amount of allergen liquid into the inner skin of the patient’s forearm, if the patient is allergic to the allergen, red and swollen mounds of a certain diameter will appear at the skin test site, as well as other accompanying symptoms; 3, patch test: commonly used for the detection of chemical components as allergens. The allergenic substance to be tested can be placed on a 1cm-sized four-layer gauze, applied to the skin of the back and inner forearm, covered with 2cm² of non-ventilated cellophane or wax paper, and then fixed with a larger adhesive tape to observe whether the skin of the test site appears itchy or painful and other positive reactions, which are generally gradually increasing. If the positive reaction gradually disappears after removing the test substance, it is a false positive, which may be related to the test time, improper operation or the patient taking other drugs, and should be carefully tested again.