Treatment depends on the cause of the rash:
Infections — Bacterial infections are treated with antibiotics. Fungal infections are treated with antifungal medications. Many viral infections that cause rash will go away within several days and require no medication. Less often, antiviral drugs are necessary.
Allergic reactions — A severe allergic reaction is a life-threatening medical emergency. It must be treated immediately with epinephrine, a medication that opens narrowed airways and raises dangerously low blood pressure. High doses of corticosteroids and antihistamines also are used to suppress the immune system's reaction. Localized allergic reactions can be treated with topical or oral corticosteroids, antihistamines and ice to relieve the itching and swelling.
Local irritants — Diaper rash is treated by changing diapers frequently and using nonprescription creams or ointments that contain zinc oxide and mineral oil.
Poisonous plants — The skin should be flushed thoroughly with warm water to remove the allergenic substance. Only then should you lather with soap and water. If you use soap immediately before flushing the skin with water, you are apt to spread the allergenic plant oil over your skin. Once you have washed off the oil, it cannot spread. The rash is often treated with prescription topical steroids. However, oral steroids may be needed for extensive rashes or rashes on the face.
Autoimmune disorders — These illnesses are treated with corticosteroid and immunosuppressive drugs, medications that suppress the patient's overactive immune system.