常見ge病~你地都可能有試過 但唔知係咩病~

你可能指rash(疹) http://en.wikipedia.org/wiki/Rash

A rash is a change in the skin which affects its appearance or texture. A rash may be localized to one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, 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 presence of a rash may aid diagnosis of the patient's condition. Not only the appearance and sensation of the rash but also the distribution (which parts of the body are affected and where it arose and spread to) and evolution of the rash may be important as certain patterns of rashes and their associated signs and symptoms are diagnostic of certain diseases. For example, the rash in measles is an erythematous, maculopapular rash that begins a few days after the fever starts; it classically starts at the head and spreads downwards.

Common causes of rashes include:

* anxiety
* allergies, for example to foods, dyes, medicines, insect stings; such rashes are often called hives Some people are sensitive to metals such as zinc or nickel
* skin contact with an irritant
* infection, e.g., by the viruses that cause chickenpox, smallpox, and measles.
* reaction to vaccination
* skin diseases such as eczema or acne
* autoimmune disorders such as psoriasis
* cancer or other disease
* pregnancy
* exposure to sun (sunburn) or heat
* lead poisoning
* irritation such as (in some cases) clothing or denim is rubbed upon the skin.

To response to above answer, any thing causing reddness of skin is called rash, so your answer dose not help any and do not point to any diagnosis.

That is urticaria (蕁麻疹 or what you called 風 '難')
It is a type of allergic response of skin. Some patient may found some things (allergen) could cause his/her urticaria. But most patients unable to found an allergen, then this is called idiopathic urticaria. ( idiopathic=自發的/原發的).
The allergen may be 1. something you eat( eg food, drug). 2 someting you applied to your skin(eg soap, cosmetics, rain) 3. something you inhaled (eg volatile chemicals for decoration) . 4. Sweat 5. physical stimulations (eg sun shine/wind) (no 3-5 are uncommon/rare but possible)

Scratching of skin can intensify the allergic response, this is a kind of reflex response.

2006-10-26 05:48:26 補充：
wrong answer