Phototoxic contact dermatitis
Phototoxic contact dermatitis is a sunburn-like skin disorder resulting from direct tissue damage following the ultraviolet light-induced activation of a phototoxic agent. Common phototoxic agents include tetracylines, antiarrhythmics such as amiodarone, diuretics such as furosemide and chlorothiazide, nonsteroidal anti-inflammatory drugs such as piroxicam and naproxen, phenothiazines and psoralens. Plants containing furocoumarins such as yarrow, parsley and milfoil may lead to phytophotodermatitis in combination with UV irradiation.
Clinical picture: Lesions develop within hours of exposure to the phototoxic agent and radiation. Erythema, oedema and burning are characteristic features, as well as vesicles and bullae in more severe cases. Rare manifestations of phototoxic contact dermatitis present as photo-onycholysis, slate-gray hyperpigmentation (due to amiodarone and tricyclic antidepressants) and lichenoid eruptions (reported with quinine and quinidine).
Distribution: Sun-exposed areas with contact to the phototoxic agent are affected.
Diagnosis: Patient history regarding exposure to potential phototoxic agents and a careful examination of the clinical features (distribution of the lesions, sparing of sun-protected areas) are mandatory. Cutaneous irradiation phototesting and photopatch testing may exlude a photoallergic dermatitis, although a negative outcome does not completely exclude the diagnosis.
Differential diagnoses: Photoallergic contact dermatitis, allergic contact dermatitis including airborne contact dermatitis, other photodermatoses such as polymorphic light eruption, chronic actinic dermatitis and erythropoetic protoporphyria must be taken into account.