Current technical means are unable to identify all allergens, and there are 2,000-3,000 allergens that can be identified. In the process of treating allergies, doctors usually try to find allergens, among which those related to diet, breathing and contact can usually be detected: 1. Ingested allergens: animal protein foods such as milk, eggs, fish, shrimp, crab, lamb, beef, pork, chicken and other poultry; oil crops, nuts, cereals, fruits and vegetables, food coloring, preservatives, etc., can also cause allergies, mostly Through the diet, but some highly food allergic people can also cause disease through the inhalation route; 2, inhalation allergens: allergic substances by inhalation and cause allergic reactions, such as pollen, willow, dust, mites, animal dander, oil smoke, paint, car exhaust, gas, cigarettes, etc., in addition to inducing respiratory reactions, can also cause discomfort outside the respiratory tract; 3, contact allergens: such as cold air, hot air, ultraviolet light, radiation, cosmetics, etc. hot air, ultraviolet light, radiation, cosmetics, shampoo, etc., can lead to allergy through contact; 4, other: for example, penicillin, streptomycin, xenogeneic serum and other injectable allergens, can also lead to allergic reactions in the body. Usually hospitals can only detect 20-30 common allergens in daily life through skin prick and venous blood sampling, and rare allergenic substances are not included. It is important to note that allergen screening is generally not recommended for infants and children under the age of 3, as they are more sensitive to external stimuli and can gradually show tolerance as they grow and develop. Patients should avoid allergens on a daily basis, and those who are unable to identify specific allergens can avoid allergen-causing items and environments as appropriate to their own situation.