Contact allergy is an allergic skin reaction from contact with a substance that is usually harmless to others. The commonest manifestation is an itchy rash that develops over a few days, after skin contact with a substance. The affected area first becomes itchy, then red and swollen with vesicles (water bubbles). Although usually confined to the area of contact, sometimes strikingly so, the rash can spread to other parts of the body. Occasionally the rash is more chronic, manifesting as an itchy patch that does not heal for weeks or even months. This usually occurs when there is frequent contact with the substance e.g. a watch strap . The rash resulting from contact allergy is called allergic contact dermatitis.
A substance that can cause contact allergy is called a contact allergen. Common contact allergens are:
1) metals e.g. nickel in watch straps, chrome in cement
2) skin care products e.g. fragrances, lanolin
3) medication e.g. flavine, neomycin.
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