Urticaria and angioedema are reactions in the skin and underlying skin tissue to histamine and other chemicals released by specialised cells called mast cells. Histamine is released in response to an invading substance your body perceives as dangerous (allergens).
Insect stings or bites
Drugs such as penicillin or aspirin
Unwitting long-term use of a food additive, preservative or food colourant, such as tartrazine (rare)
Infections – hives sometimes follows viral infections such as hepatitis, infectious mononucleosis (glandular fever), and German measles.
Certain foods, particularly eggs, shellfish, nuts and fruits. Sometimes hives erupt suddenly after you’ve eaten a tiny amount of a food. Other times, hives occur only after eating large amounts (for example, strawberries).
Keep a detailed diary of everything you eat, drink, take, or are exposed to for two to four weeks
Avoid foods, one at a time, to which you think you may be allergic
See an allergist for skin tests (although seldom helpful)
When to see a doctor