Itching

From: www.wikipedia.org

Causes

Scabies is one cause of itching.
Itching can be caused by:
Head lice, if limited to the neck and scalp.
Pubic lice, if limited to the genital area.
Body louse. Body lice can be seen in substandard living conditions.
Urticaria Urticaria (also called hives) usually causes itching.
Xerosis (dry skin). This is the most common cause,[citation needed], frequently seen in the winter and also associated with older age, frequent bathing in hot showers or baths, and high-temperature and low-humidity environments.
Skin conditions (such as psoriasis, eczema, sunburn, athlete's foot, hidradenitis suppurativa and many others). Most are of an inflammatory nature.
Scab healing; scar growth; and the development or emergence of moles, pimples and ingrown hairs from below the epidermis.
Insect bites, such as those from mosquitos or chiggers.
Allergic reaction to contact with specific chemicals, such as Urushiol, derived from Poison Ivy or Poison Oak.
Hodgkin's disease.
Jaundice. (Bilirubin is a skin irritant at high concentrations.)
Polycythemia, which can cause generalized itching due to increased histamine.
Punctate palmoplantar keratoderma.
Scabies especially when several other persons in close contact also itch.
Thyroid illness.
Hyperparathyroidism.[13]
Shaving, which may irritate the skin.
Uraemia.
Diabetes Mellitus.
Dandruff. (An unusually large amount of flaking is associated with this sensation.)
Iron deficiency anemia.
Parasitic infections. (including but not limited to head lice, body lice, scabies, pubic lice, etc)
Psychiatric disease.
Medication:
Allergy - (due to reaction of an individual's immune system to certain chemical compounds)
Photodermatitis – (sun)light reacts with chemicals in the skin, leading to the formation of irritant metabolites
Directly (e.g. morphine and other opiates)
Chloroquine.
Cholestasis
Related to pregnancy:
Obstetric cholestasis (see http://www.patient.co.uk/showdoc/23068933/)
Pruritic Urticarial Papules and Plaques of Pregnancy (PUPPP)
Gestational pemphigoid
Malignancy or internal cancer such as lymphoma.[14]

[edit] Treatment
Main article: Antipruritic
A variety of over-the-counter and prescription anti-itch drugs are available. Some plant products have been found to be effective anti-pruritics, others not. Non-chemical remedies include cooling, warming, soft stimulation.

[edit] Common antipruritics
Topical antipruritics in the form of creams and sprays are often available over-the-counter. Oral anti-itch drugs also exist and are usually prescription drugs. The active ingredients usually belong to the following classes:
Antihistamines such as diphenhydramine (Benadryl)
Corticosteroids such as hydrocortisone topical cream, see topical steroid
Local anesthetics such as benzocaine topical cream (Lanacane)
Counterirritants, such as mint oil, menthol, or camphor[15]
Crotamiton (trade name Eurax) is an antipruritic agent available as a cream or lotion often used to treat scabies. Its mechanism of action remains unknown.
Phototherapy is helpful for severe itching, especially if caused by renal failure. The common type of light used is UVB.[16]
Sometimes scratching relieves isolated itches, hence the existence of devices such as the back scratcher. Often, however, scratching can intensify itching and even cause further damage to the skin, dubbed the "itch-scratch-itch cycle".
The mainstay of therapy for dry skin is maintaining adequate skin moisture and topical emollients.