The essence of asthma is chronic allergic inflammation of the airways, and it is now believed that the majority of bronchial asthma is allergic, probably more than 80% for children, and about half of adults are allergy-related. Long-term exposure to a large number of allergens is the main reason for recurrent asthma attacks and yearly aggravation of the disease. Identifying allergens and avoiding exposure to them is the key to the prevention and treatment of allergic asthma. An allergic reaction is a super-normal reaction of the body to one or more substances, some of which are harmless to most people. The main reason for this is that the patient’s body produces too much immunoglobulin E (IgE), which can react with allergenic substances (allergens) in the environment and stimulate the body to release certain excessive chemicals and subsequently produce various symptoms. There are two general methods of detection, one is by blood test, which is to determine the level of antibody IgE in the patient’s body to determine the patient’s allergens. The other is by skin prick test. What are the common allergens? There are many things in our life that can become allergens, such as breathing in, eating in, direct skin contact, and injecting in, such as house dust, dust mites, pollen, plant hair, animal hair, formaldehyde, pesticides, perfume, disinfectant, artemisia, fish, shrimp, crab, some vegetables, fruits, drugs, and even milk, beans, flour, eggs, etc. All of these can become allergens. Although there are many allergens in nature, as long as we know what we are allergic to and pay attention to avoid it, it is not terrible.