Onion allergy is a kind of food allergy, the attack can appear coughing, sneezing and other respiratory system manifestations, in addition to skin symptoms, gastrointestinal symptoms and so on. 1. Respiratory symptoms: runny nose, nasal congestion, sneezing, coughing, wheezing, muffled voice and other symptoms, and in severe cases, respiratory difficulties. 2. Skin and mucous membrane symptoms: common manifestations include skin erythema, papules, and wind bumps, accompanied by obvious itching. 3. Digestive system symptoms: including diarrhea, abdominal pain, vomiting, etc., and in severe cases, blood in the stool. If the above allergic symptoms occur, it is recommended to go to the hospital in time.