One of the drugs commonly used to treat hyperuricemia and gout, allopurinol, is an inexpensive, effective drug that is often used clinically. However, it is important to be alert to the side effects of this drug. Adverse drug reactions to allopurinol include: gastrointestinal symptoms, rash, liver damage, and bone marrow suppression. In particular, allopurinol hypersensitivity syndrome. Hypersensitivity reactions to allopurinol do not occur with the first dose, but occur within the first few months of using this drug. The most common is exfoliative dermatitis, which is more likely to occur in patients with combined use of thiazide diuretics and renal insufficiency. Once it occurs, the mortality rate is high. In some Asian countries and regions, the use of allopurinol in Asian populations requires caution against this severe allergy, and is currently strictly prohibited in patients who are HLA-B*5801 positive. Many medical institutions in China are already able to check this item, and the test needs to be performed before using allopurinol to avoid lethal and severe allergies.