Allergic Contact Dermatitis

Allergic Contact Dermatitis is an itchy skin condition caused by an allergic reaction to material in contact with the skin. It is distinct from irritant contact Dermatitis, in which a similar skin condition is caused by excessive contact with irritants.

Allergy is the term given to a reaction by a small number of people to a substance (known as the allergen), which is harmless to those who are not allergic to it. Only small quantities of allergen are necessary to induce the reaction. Contact allergy occurs predominantly from the allergen on the skin rather than from internal sources or food. The first contact does not result in allergy; often the person has been able to touch the material for many years without adverse reaction.

Clinical features of allergic contact dermatitis

The Dermatitis is generally confined to the site of contact with the allergen, although severe cases may extend outside the contact area or it may become generalised. Sometimes the allergen is transmitted from the fingers so unexpected sites can be affected e.g. the eyelids and genitals. Dermatitis is unlikely to be due to a specific allergen if the area of skin most in contact with that allergen is unaffected.

Some typical examples of allergic contact Dermatitis include:

• An eczema of the wrist underlying a watch strap due to contact allergy to nickel.
• An eczema of the lower leg when ankle strapping has been removed due to contact allergy to colophony in the adhesive plaster.
• Hand Dermatitis caused by an anti-oxidant chemical used in the manufacture of rubber gloves.
• Itchy red face due to contact allergy with a preservative in a moisturizer.
• Contact allergy arises only after the skin has been exposed to ultraviolet light.

If you think you may have a contact allergy, consult a dermatologist to have patch tests performed.

Treatment of allergic contact dermatitis

It is important to recognize how you are in contact with the responsible substance so that, where possible, you can avoid it.

• Find out precisely what you are allergic to by having comprehensive patch tests.
• Identify where the allergen is found.
• Carefully study your environment to locate the allergen. Note: many chemicals have several names, and cross-reactions to similar chemicals with different names are common.
• Ask your dermatologist to help.

Active Dermatitis is usually treated with the following:

• Emollient creams (mositurisers)
• Topical steroids (cortisone creams)
• Topical or oral antibiotics for secondary infection
• Oral steroids, usually short courses, for severe cases
• Phototherapy (UV light)

View photos of allergic contact dermatitis >>

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