Both irritants and allergens can induce contact dermatitis. Non-allergic dermatitis sometimes follows isolated exposure to a strong irritant or, more frequently, is induced by repeated exposure to less potent chemicals, including soaps, detergents and solvents. The skin becomes dry, inelastic, fissured and secondarily infected through breaches in the protective stratum corneum.

Allergic contact dermatitis is a form of delayed hypersensitivity. It is, in part, genetically determined and results from exposure of a previously sensitized individual to an allergen. A vesicular or bullous eruption usually first develops at the site of primary contact but the allergen is frequently transferred by the hands to other parts of the body. The margins of the affected areas are often unnaturally sharp and angular. Inflamed, damaged or diseased skin is especially vulnerable, whereas the scalp, the palms of the hands, and the soles of the feet are protected by the greater thickness of the stratum corneum.

Plants, dyes, nickel and other metals, rubber, cosmetics and topical medicines are all potential allergens. Causative agents may be identified by patch testing, but the correct interpretation of such tests may be difficult. Sensitization to a component of a topically applied medicine is not uncommon and should be suspected if dermatitis develops following the application of a topical agent.

Prevention and management

Emollient creams accelerate healing and barrier creams may offer protection in the workplace. Patients should not use abrasive soaps and they should avoid, as far as possible, exposure to irritant substances.

Hydrocortisone 1% ointments or creams are of value in suppressing inflammation. More potent topical corticosteroids can also be used, but may not offer any better efficacy since the condition is usually self-limiting. The use of a short course of oral prednisolone or prednisone to suppress severe acute reactions associated with blistering, exudation and oedema should be considered. The oral corticosteroid can be given in successively lower doses over a 2-week period. Consultation with a dermatologist, if one is available, should be considered.