Topically applied methoxsalen solution photoactivated by blacklight was combined with a low-strength anthralin paste regimen for the treatment of resistant psoriasis. Initial trials resulted in complete clearing at test sites within one to three weeks, while recalcitrant lesions at control sites remained relatively unaffected. The authors suggest a type of synergism is produced analogous to modern cancer treatment where chemotherapy and selective irradiation are combined to effect control.
Willis I, Harris DR. Resistant PsoriasisCombined Methoxsalen-Anthralin Therapy. Arch Dermatol. 1973;107(3):358-362. doi:10.1001/archderm.1973.01620180012003