Itch
From Wikipedia, the free encyclopedia
| ICD-10 | L29. |
|---|---|
| ICD-9 | 698 |
| DiseasesDB | 25363 |
| MedlinePlus | 003217 |
An itch (Latin: pruritus) is a sensation felt on an area of skin that causes a person or animal to desire to scratch that area. It is a distressing symptom that can cause discomfort. Scratching may cause breaks in the skin that may result in infection. Itching can be related to anything from dry skin to undiagnosed cancer.
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[edit] Mechanism
The central chemical involved in itching is histamine, a molecule released by mast cells in the skin. Histamine is the chemical that causes the itch and reddening when bitten by insects. It binds to local nerve endings on specific receptors.
An itch from cutaneous (skin-related) stimuli, such as movement of small hairs on the body, was thought to be transmitted along the same pathway as pain, although recent research has found that itching has its own neural pathways. An itch caused by histamine is transmitted to the brain by a different neural pathway, described in 2001 by Andrew et al. As with pain, a histamine-induced itch travels via the spinothalamic tract, but in fibres specific for itch.
[edit] Causes
The feeling of itchiness can be caused by a movement of hairs 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.
Common causes for itching can be:
- Xerosis. This is the most common cause, frequently seen in winters, associated with advanced age, frequent bathing particularly hot showers, hot baths, and high temp and low humidity environment.
- Skin conditions (such as psoriasis, eczema, sunburn, athlete's foot 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
- Diabetes Mellitus
- HIV
- Iron deficiency anemia
- Psychiatric
- Medication:
- Allergy
- Photodermatitis – (sun)light reacts with chemicals in the skin, leading to the formation of irritant metabolites
- Directly (e.g. morphine)
[edit] Treatment
Itching can be treated directly with an antipruritic. Ice can also be helpful. 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".
A number of plants are traditionally seen as natural remedies for itch. For itch caused by mosquito bites, stinging nettles, or poison ivy in the woods, one may use the juice of the Jewelweed plant. Another remedy is Dock, traditionally used for nettle stings. These traditional remedies often conveniently grow in the areas where the cause (mosquitos, poison ivy, nettles, etc.) is common.
The mainstay of therapy for dry skin is maintaining adequate skin moisture and topical emollients.
[edit] See also
[edit] Related to pregnancy
[edit] References
- Andrew D, Craig AD (2001). Spinothalamic lamina I neurons selectively sensitive to histamine: a central neural pathway for itch. Nature Neuroscience Jan;4(1):9-10.
- National Cancer Institute (2003) "Pruritus" Retrieved Aug. 22, 2005.
