The patch test is the most classic and reliable method for detecting exposure to allergens, and is a test that can detect or identify allergic skin disease allergens. It is based on the principle of skin allergic reaction, standardized suspected allergens, sequentially applied to the patient’s back skin, after 48 hours of removal, can induce local skin reactions, in 72 hours based on local skin performance interpretation of the results. Through this test, the causative agent of the patient can be found, providing new treatment ideas; reducing the chance of patient’s missed diagnosis; facilitating the discovery of new allergens. And guide patients to take appropriate measures to effectively avoid exposure to allergens. This improves the level of diagnosis, clarifies the causative factors early, in order to achieve both the symptoms and the root cause of the disease, so that the disease is cured as soon as possible, reducing recurrence, improving the quality of life of patients, eliminating the waste caused by unknown diagnosis and blind treatment, and saving the cost of treatment for patients. In modern society, with the development of the economy and the improvement of living standards, the rapid development of industry, the rise of various manufacturing industries, environmental pollution is becoming increasingly serious, people are exposed to more and more allergens, such as: a variety of civil engineering, home decoration materials, dyes, food and cosmetic additives, preservatives, plastics, rubber products, an endless array of daily detergents, and so on, even in our daily lives we are easy to ignore but Allergens are complex and diverse, and the incidence of allergic diseases is increasing, and the causes are becoming more and more complex. Therefore, the need for allergen testing has become increasingly important. The patch test is used for the following diseases: contact dermatitis, atopic dermatitis, eczema, chronic urticaria, acne, erythema multiforme, allergic purpura, rash-like rash, lichen planus, psoriasis, erythroderma, maculopathy, allergic rhinitis, asthma, allergic conjunctivitis, and certain occupational diseases. In addition, the test is a skin test, simple and non-invasive, painless for the patient, and without significant adverse reactions.