The treatment will be meaningless if you continue to contact with substance that causes allergic reactions. So first analyze your diet and try to figure out what was the cause of the allergic rash. Maybe the food had nothing to do, and the culprit is any tool or household chemicals. Also cause of rashes can be a medication, dust, hair, etc. If you are having trouble finding allergen, consult your doctor for special tests.
Eliminate the impact of the allergen on the body and only then proceed to drug therapy. Take antihistamines recommended by the allergist. In some cases, preferred proven "Suprastin" or "Tavegil", but sometimes it's better to take a more modern medicines that do not cause side effects. These include "claritin", "Core", "Zyrtec", "Telfast" and others.
To relieve itching and inflammation that often accompany allergic rashes, use local means, for example, the cream "Elidel", "Fenistil gel" or hormonal ointments on the basis of hydrocortisone.
Strengthen your immune system, because it determines the body's ability to resist various unfavorable factors. To completely get rid of allergies is, of course, will not help, but the intensity of the rashes will reduce. In the absence of allergies to drugs take vitamin supplements. If you are sensitive to it stick to tempering procedures.
As an additional measure, use cool compresses, take a contrast shower. Due to this the blood vessels are narrowed, which will have a short-pruritic effect.