The feeling of itchiness can be caused by a movement of hair or the release of a chemical (histamine) from cells under the skin. Itchiness is regarded as protective, as it helps creatures remove parasites that land on their skin.

Itching can be caused by:

Xerosis (Winter Itch). This is the most common cause, frequently seen in winters. 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.

Insect bites, such as those from mosquitos or chiggers.

Allergic reactions to contact with specific chemicals, such as Urushiol 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

Scabies or infection with lice or worms

Thyroid illness

Shaving, which may irritate the skin

Diabetes Mellitus


Pain and itch have very different behavioral response patterns. Pain evokes a withdrawal reflex which leads to retraction and therefore a reaction trying to protect an endangered part of the body. Itch creates a scratching reflex which draws one to the affected skin site. For example, responding to a local itch sensation is an effective way to remove insects on the skin. Scratching has traditionally been regarded as a way to relieve one self by reducing the annoying itch sensation. However there are hedonic aspects of scratching as one would find noxious scratching highly pleasurable. This can be problematic with chronic itch patients, such as ones with atopic dermatitis, who may scratch affected spots until it no longer produces a pleasant or painful sensation instead of when the itch sensation disappears. It has been hypothesized that motivational aspects of scratching include the frontal brain areas of reward and decision making. These aspects might therefore contribute to the compulsive nature of itch and scratching.

some itch information courtesy of Wikipedia, see more here