The occurrence and development of many skin diseases are clinically related to exposure to allergens, such as urticaria, atopic dermatitis and eczema, etc. Clinical treatment is mainly symptomatic and can relieve symptoms, but some patients are not free from exposure to allergens, resulting in recurrent and prolonged disease, so for patients with frequent allergies can do an allergen screening, and if the allergen is found, it can avoid the occurrence of allergies from the root. Common methods of allergen testing include serum allergen antibody screening, prick test and patch test. 1, serum allergen antibody screening: generally includes ingestion and inhalation group testing, suitable for urticaria, atopic dermatitis, eczema and allergic rhinitis, etc., a one-time blood sampling is simple and easy. 2, puncture test: similar to the detection range of serum allergen antibody screening, especially suitable for urticaria allergen screening, but the accuracy is poor in patients with positive skin scarring. 3, patch test: most suitable for the detection of contact allergens, such as contact dermatitis, cosmetic dermatitis, solar dermatitis, eczema, etc., for the above allergic diseases is the gold standard for diagnosis. Any allergen screening requires the discontinuation of antihistamines for 3-7 days and the systematic application of glucocorticoids for 2 weeks to avoid interference with the test results.