Urticaria (nettle rash) consists of hives or general redness. It may be either a)acute (sudden onset) or b)chronic.
Acute urticaria e.g. peanuts, seafood and medication can normally be diagnosed from the history and Allergy testing.
Chronic urticaria is more complex with many aggravating factors including food, other illnesses, reduced immunity and also aggravated by physical factors e.g. contact, heat, sweating, exercise.
Diagnosis and management of urticaria requires a detailed history and Allergy test if indicated. Food can also aggravate urticaria through non-allergic mechanisms. Blood tests are required if symptoms are persistent or associated with other signs of ill health. Foods can affect this condition but not always by an allergic mechanism.