How can you tell whether you have hives or allergic reactions?

Histamine driven. Hives (or welts) are histamine driven reactions. These lesions come and go within hours and do not leave scales or marks. Hives can be a form of allergic reaction (ie to drugs or shellfish), but they can often be idiopathic (unknown trigger). Because we know this is a histamine driven problem, we treat with oral antihistamines, or oral steroids if severe and associate with wheezing.
Hives is swelling. Hives is swelling with no rash. Hives are caused by a reaction to food, drug, or infection.There are also physical hives to cold , heat, or exercise.