Food additives and preservatives may also cause hives. Hives may appear within minutes or up to two hours after eating, depending on where the food is absorbed in the digestive tract. Diet supplements, antacids, arthritis medication, vitamins, eye and eardrops, laxatives, vaginal douches, or any other non-prescription item can be a potential cause of hives. If you have an attack of hives, it's important to tell your doctor about all of the preparations that you use to assist in finding the cause. Many infections can cause hives.
Colds are a common cause of hives in children.
The cause of this type of hives is usually much more difficult to identify than that of acute urticaria. In patients with chronic urticaria, the cause is found in only a small number of patients. Your doctor will need to ask many questions in an attempt to find the possible cause. Since there are no specific tests for hives, testing will depend on your medical history and a thorough examination by your dermatologist. Physical Urticarias Hives can be caused by sunlight, heat, cold, pressure, vibration, or exercise.