Clinical presentation

This is the commonest photodermatosis, and women are affected twice as frequently as men. Pruritic urticated papules, plaques and vesicles develop on light-exposed skin usually about 24 h after sun or artificial ultraviolet (UV) exposure (Fig. 1). It starts in the spring and may persist throughout the summer. The degree of severity is variable.

Fig. 1 Polymorphic light eruption affecting the lower legs.

Differential diagnosis and management

Photoallergic contact dermatitis, drug-induced photosensitivity and lupus erythematosus may need to be considered in the diagnosis of polymorphic light eruption.

The first-line therapy is to use sunscreens and protective measures. A short course of UV therapy (UVB or PUVA) in the late spring can ‘harden’ the skin so that the patient is able to have a disease-free summer.

Clinical presentation

There is often a long history of a chronic dermatitis that evolves into a photodermatitis, or a photoallergic contact dermatitis may have been present from the outset. Lichenified plaques of chronic dermatitis form on light-exposed sites and beyond, and are worse in the summer, although the eruption tends to become perennial (Fig. 2). The patients are sensitive to the UVA and UVB wavelengths and often to visible light as well. They may also have a contact or photocontact sensitivity to plant sesquiterpene lactones (airborne allergens) or to cosmetic ingredients, although the contribution of this to the overall picture is unclear.

Fig. 2 Chronic actinic dermatitis involving the light-exposed areas of the face.

Differential diagnosis and management

Airborne contact dermatitis or drug-induced photosensitivity may need to be considered, but there is normally little doubt about the diagnosis. Phototesting is helpful.

Light avoidance, sunscreens and topical steroids are used at first in the management of chronic actinic dermatitis. Subsequently, azathioprine, ciclosporin, mycophenolate or systemic steroids may be necessary.