If an allergic reaction occurs, the patient can consider the following aspects: Season: allergy symptoms appear with the seasonal changes, often related to insect and pollen allergies Food: which foods to eat will produce allergy symptoms, and how long to consume allergy symptoms Pets: whether to keep pets, and what pets to keep after the allergy symptoms Residential environment: humid and unventilated homes are prone to breeding dust mites and molds. Occupation: you can come into contact with allergens such as chemicals, paints, spices, sawdust, etc., and long-term contact can easily induce allergic reactions. There are two ways to check allergens in the allergy department of the hospital: 1) in vitro test, i.e. blood test for allergens; 2) in vivo test, i.e. allergen spotting test and patch test. The precautions for checking allergens: 1, blood test: fasting to draw blood, recently due to a shortage of reagents (imported reagents) within a month of the suspension of the test to about November can begin to check. Allergen prick test: do not take oral or static hormone drugs and antihistamines such as Keratan, Ketotifen, Paracetamol, Segundine, etc. within 1 week before the examination.