If there is associates itching, it could be Hives, which develop in response to an allergic reaction, by the release of histamine. The allergen
can be medications, food, extremes of temperature, exercise and viral infections to name a few. Consult an allergy specialist. First he may do a blood IgE levels to see if they are raised. Next, he will do skin testing. This test is painless, in which a very small amount of certain allergens are pricked into the surface of your skin.