If you have a history of allergy your doctor must be informed. Just by looking at the skin a doctor can tell if the patient is afflicted with hives.
Sometimes, the causative agent is easily identifiable because an allergic reaction happens as soon as the agent is touched or eaten.
If the hives are appearing for the first time, skin tests or blood tests may be done to confirm the allergic reaction and to identify the allergen. A complete medical history and family history of the patient will be taken.
The patient will be also be advised to keep a food diary to help in identifying the triggering agent.
In majority of the instances the cause of the hives will always remain a mystery and in such a case the term idiopathic hives is used.