Pruritus is another word for itching, and itching may be caused by something in contact with the skin, such as an insect, by skin diseases such as eczema, and by some more general illnesses which are not specific to the skin, such as kidney failure. An itch usually provokes the desire to scratch, but excessive scratching can damage the skin, leading to infection. A common cause of pruritus, especially in older people, is dry skin, which can be treated with moisturizers.
Causes of pruritus can range from harmless ones, such as insect bites, to serious diseases like cancer. In some conditions, the itch is confined to one area of the body, with one example being hand eczema. Here, dry skin on the hands develops into itchy lumps and blisters, and ultimately the skin becomes cracked, swollen and sore, with the possibility of infection occurring. Hand eczema is typically treated with a short course of steroid ointment, together with moisturizing creams and avoidance of detergents and irritating chemicals, perhaps by the use of gloves.
In another common, localized form of pruritus, known as pruritus ani, the anus becomes unbearably itchy. It is characteristically more itchy after opening the bowels or during the night. This unpleasant sensory experience can be treated by attention to personal grooming, keeping the affected region scrupulously clean and dry, by modifying the diet to avoid spicy or acidic foods and by applying ointments to soothe the area. Sometimes a short course of a steroid ointment is also prescribed.
When general, or systemic, diseases are involved in causing pruritus, the itching can be quite mild or extremely severe. In around half of people with long-term, or chronic, kidney failure, itching occurs every day, and this can consist of recurrent episodes or it may be constantly present. Although the cause is not fully understood, it is known that the sensation often becomes worse after dialysis or at night. The head, trunk and arms are the most common places for pruritus to be experienced. Treatment of the itching mainly consists of ultraviolet light phototherapy, where the patient stands inside a lightbox.
Pruritus is associated with a type of cancer called Hodgkin disease, or Hodgkin's lymphoma, where a malignant growth in the lymphatic system causes abnormalities of blood cells. As well as itching, symptoms of night sweats and weight loss may occur, and there may be an enlarged lymph gland, a swollen spleen, and pigmented and dry skin. A combination of chemotherapy and steroids has been shown to relieve the itching in some cases.