There are many types of skin rashes that cause itching, such as those that result from irritation or allergic reactions, according to Mayo Clinic. Rashes that result from skin conditions such as psoriasis, eczema, scabies and hives as well as rashes caused by insect bites can also cause itching.
Treatment for itchy skin can begin once the cause of the irritation is identified, states Mayo Clinic. For example, if a rash develops as a result of an allergic reaction, a doctor might suggest taking an oral antihistamine. Some types of antihistamines, such as Benadryl, cause drowsiness; others, such as Zyrtec and Claratin, do not. Antihistamines that cause drowsiness may be useful when patients are unable to sleep at night due to itching. Corticosteroid creams are also effective in treating rashes that cause itchy skin.
Rashes that occur as a result of skin conditions can usually be treated with over-the-counter medicines that contain hydrocortisone, according to WebMD. For more severe cases, one may have to use prescription-strength hydrocortisone, which comes in a variety of forms, such as creams, pills and injections. Rashes that are caused by insects, such as lice, can be treated with over-the-counter or prescription medicine, but they may linger a few days as the initial allergic reaction subsides.