What is skin allergy? (Introduction)

Skin allergy is an abnormal reaction of the skin to a substance that is usually harmless. The immune system treats the substance (the allergen or irritant) as a threat and responds with inflammation, causing itching, redness, rashes, swelling or blisters. It is very common and affects people of all ages, and many cases are mild and manageable.

What it includes "Skin allergy" is an everyday term that covers several conditions:

• Contact dermatitis, from touching a substance such as nickel, cosmetics, plants or detergents.
• Urticaria (hives), with itchy raised welts that come and go.
• Atopic dermatitis (eczema), a long-term itchy, dry skin condition that often runs in families.
• Angioedema, swelling of deeper skin layers, often of the lips, eyelids or face.
• Drug and food related rashes.

Why it happens Some reactions are true allergies, in which the body makes antibodies to the allergen. Others are irritant reactions that damage the skin directly, without the immune system. The treatment depends on which one it is.

Who gets it People with a personal or family history of allergies, asthma, hay fever or eczema are more likely to develop skin allergies. Jobs that involve wet work, chemicals or cosmetics also raise the risk.