A rash is a change of the human skin which affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell, and may be painful. The causes, and therefore treatments for rashes, vary widely. Diagnosis must take into account such things as the appearance of the rash, other symptoms, what the patient may have been exposed to, occupation, and occurrence in family members. The diagnosis may confirm any number of conditions. The presence of a rash may aid diagnosis; associated signs and symptoms are diagnostic of certain diseases. For example, the rash in measles is an erythematous, morbilliform, maculopapular rash that begins a few days after the fever starts. It classically starts at the head, and spreads downwards. Differential diagnosis
Common causes of rashes include:

Food allergy
Medication side effects
Anxiety
Allergies, for example to food, dyes, medicines, insect stings, metals such as zinc or nickel; such rashes are often called hives. Skin contact with an irritant
Fungal infection, such as ringworm
Balsam of Peru
Reaction to vaccination
Skin diseases such as eczema or acne
Exposure to sun (sunburn) or heat
Friction due to chafing of the skin
Irritation such as caused by abrasives impregnated in clothing rubbing the skin.
Erythrokeratodermia variabilis (also known as "erythrokeratodermia figurata variabilis", "keratosis extremitatum progrediens", "keratosis palmoplantaris transgrediens et progrediens",: 509  "Mendes da Costa syndrome", "Mendes da Costa type erythrokeratodermia", and "progressive symmetric erythrokeratoderma") is a rare autosomal dominant disorder that usually presents at birth or during the first year of life. To date, it is thought to be caused by mutations in genes encoding for connexin channels proteins in the epidermis, leading to the misregulation of homeostasis in keratinocytes.One type is characterized by generalized, persistent, brown hyperkeratosis with accentuated skin markings, while a second type is localized, with involvement that is limited in extent and characterized by sharply demarcated, hyperkeratotic plaques. : 565 It can be associated with GJB3 and GJB4. It was characterized in 1925. See also
List of cutaneous conditions


== References ==