Topical methoxsalen and blacklight in the treatment of psoriasis.

Thirty patients with recalcitrant psoriasis were treated with topical methoxsalen and blacklight (UVA). A 1% concentration either in an acetone, alcohol, propylene glycol vehicle, or hydrophilic ointment, USP, applied two hours before light exposure was highly effective. Twelve patients were completely cleared and nine were markedly improved in three to five weeks. Plaque-type and guttate psoriasis responded best while exfoliative psoriasis benefitted less. Maintenance of a phototoxic reaction in the lesion was necessary for total resolution. Topical methoxsalen and blacklight is feasible for outpatient treatment of plaque-type psoriasis of limited extent.