Patients may think: skin disease is simple, rash at a glance, why do not need to test so complicated? In fact, the skin is the largest organ of our body, the most extensive contact with the outside world, is the body’s first line of defense, has a very important role. Because of this, a variety of complex factors outside the body is often we can not simply “at a glance”, coupled with individual differences in human beings, resulting in different pathological changes in the skin, prompting doctors to actively look for the cause, only to find the cause, the skin is easy to solve the problem, so medical laboratory tests become important. As we live in an environment where pollution is more aggravated, many allergic diseases such as eczema, urticaria, contact dermatitis, pruritus and other skin diseases are increasing in our daily skin clinics, and the constant itching makes them suffer, and the long-term medication makes them overwhelmed, one of which is physically unbearable, and the other is economically burdensome, so it is important to find out the cause of the itching, that is, the allergens, as soon as possible. Therefore, it is very important to find out the cause of itching, that is, the allergen, as soon as possible. Even if the result of the test is negative, it is still meaningful, indicating that the cause of allergy is not within the range of our common human allergens, such as diet can be targeted, more quality of life. Some infectious skin diseases, such as measles, chicken pox, hand, foot and mouth disease, gonorrhea, non-gonococcal urethritis, etc., can be diagnosed more clearly the earlier the test is performed, so that the course of the disease can be shortened and cured as early as possible to avoid greater damage to the body and to interrupt the infection even earlier! For some precancerous skin diseases or skin cancers, such as melanoma, seborrheic keratosis (senile plaque), basal cell carcinoma, etc., early biopsy and pathological examination can even save lives. Another example is like syphilis, AIDS, etc. Many patients have no symptoms and only find out when they donate blood, before surgery and other examinations, or even when there is serious damage to the body, and the result is too late to regret. We have such patients on hand, such as neurosyphilis causing dementia and cardiovascular syphilis causing serious heart disease death. These are heartbreaking and regrettable.