Itching without a rash is known as pruritus, and it's often treated with topical steroid creams, oral antihistamines and moisturizing lotion, explains About.com. It's also recommended that those with itchy skin that doesn't go away see a doctor.
People who have generalized pruritus, or who itch all over, may have symptoms that are caused by a number of situations, including medication use, infections, liver disease and iron deficiency, states About.com. The condition may also be caused by kidney disease, thyroid issues or certain cancers. Contact dermatitis, even without a rash, is the most common cause of generalized pruritus.
Some medications that can cause itching without a rash include morphine, Vicodin and codeine, reports About.com. Aspirin and nonsteroidal anti-inflammatory drugs may also cause itching because they affect the liver. Kidney, liver and thyroid tests are used to identify generalized pruritus when no rash is present. A complete blood count is done, as are tests for iron levels. The stool of the person may be checked for parasites, and a chest X-ray may be done to eliminate lymphoma.
In most cases, pruritus is a symptom of an underlying condition, according to About.com, and the location and severity of the itch may help a doctor determine the cause of the itching.