Benzyl salicylate (BS), a weak contact sensitizer, caused severe pruritus in six of 15 patients who applied it in a trioxsalen lotion. Delayed hypersensitivity to BS was enhanced by the phototoxic effects of methoxsalen. Only one of 14 control patients reacted to the BS.
Kahn G. Intensified Contact Sensitization to Benzyl SalicylatePhototoxic Effects of Topical Psoralen Therapy. Arch Dermatol. 1971;103(5):497-500. doi:10.1001/archderm.1971.04000170031007