Allergology (Part 7)

Allergic contact eczema Allergic contact eczema is a Coombs and Gell type IV hypersensitivity reaction (after previous sensitisation). Intact skin prevents penetration of allergens, whereas macerations (softening) of the skin due to sweating, an occlusive milieu or moisture facilitate penetration of allergens and irritant substances. Dry and inflamed skin also exhibits a disrupted dermal barrier, also facilitating penetration. In the sensitisation phase, factors such as contact allergen concentration, exposure surface area, skin condition (inflamed, chronic wounds, occluded conditions), repeated exposure to the contact allergen and its allergenic potency are important.