The sudden onset of many red bumps on the body is very itchy, consider hives, hives is caused by a variety of causes of small blood vessel dilation and increased permeability of the skin mucosa and a kind of edema reaction, the specific cause is not clear, may be related to the following factors: a. food factors, eating fish and shrimp, seafood, peanuts, tomatoes, food additives, etc. can cause allergies. Second, drug-induced, many drugs can cause allergies, such as penicillin drugs, sulfonamides, antipyretic and analgesic drugs, etc.. Third, infection factors, including bacterial infections, viral infections, parasitic infections, fungal infections, etc. Fourth, mental factors, such as mental stress can cause allergies. Physical factors, such as sunlight exposure, friction and pressure, can cause allergy. Sixth, caused by disease, such as systemic lupus erythematosus, rheumatic fever, malignant tumors, etc. can cause urticaria. Seven, other factors, too many allergens in the environment, such as pollen, dust, etc.