The doctor can check to see what one might be reacting to, but finding the exact cause may be hard. Hence, the best treatment is prevention. However, when contact with trigger cannot be avoided, usually skin rash and the itching can be eased with the right medication.
Treating allergies can involve different medications, including steroids and allergy shots, but usually the first thing to try is an antihistamine. Common antihistamine like Diphenhydramine is available in lotions as well as pill formats.
Some antihistamine pills are associated with occasional reports of drowsiness. Higher order treatment with topical steroids is also seen to be practiced by doctors. However steroids are known to have side effects such as skin thinning, skin discoloration, excessive hair growth in the area.