Contact allergic dermatitis

Allergic contact dermatitis accounts for 20% of cases of all contact dermatitis (1)

• this requires prior sensitization of the skin to a specific allergen. T lymphocytes become specially sensitised to the allergen and upon fresh contact with it, mediate a dermatitis reaction typically within 48hours
• it is an example of a type IV hypersensitivity reaction (2)
• affects 1-2% of the population

It occurs twice as frequently in women as in men, and often starts at a young age (3).

The number of children with allergic contact dermatitis is increasing. It has been suggested that children with eczematous eruptions should be patch-tested, especially children with hand and eyelid eczema (4).

Prognosis for allergic contact dermatitis is usually worse compared to irritant contact dermatitis unless the allergen is identified and avoided (2).

A common cause of this type of dermatitis is nickel.

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References:

1. Alinaghi F, Bennike NH, Egeberg A, et al. Prevalence of contact allergy in the general population: a systematic review and meta-analysis. Contact Dermatitis. 2019 Feb;80(2):77-85.
2. Rashid RS, Shim TN. Contact dermatitis. BMJ. 2016;353:i3299.
3. Peiser M et al. Allergic contact dermatitis: epidemiology, molecular mechanisms, in vitro methods and regulatory aspects. Current knowledge assembled at an international workshop at BfR, Germany. Cell Mol Life Sci. 2012;69(5):763-81.
4. Bourke J et al. Guidelines for the management of contact dermatitis: an update. BJD 2009; 160:946-954