Topical photochemotherapy with psoralen and its derivatives 
4,5',8-trimethylpsoralen (TMP) and 8-methoxypsoralen (8-MOP), with UVA 
irradiation, was evaluated with regard to minimum phototoxic dose, 
concentration, timing of UVA irradiation and systemic and local side-effects, in 
healthy volunteers. Psoralen (0.005%) in aqueous gel was found to be superior to 
TMP and 8-MOP in aqueous gel. No hyperpigmentation was seen after topical PUVA 
treatment with psoralen in aqueous gel. Patients with plaque-type psoriasis (n = 
7), palmoplantar psoriasis (n = 7) and hyperkeratotic eczema (n = 2) were 
treated. Topical PUVA therapy was effective in most psoriasis patients, without 
the occurrence of local or systemic side-effects. Moreover, hyperkeratotic 
eczema patients who did not respond to conventional therapy showed partial 
remission. These results indicate that topical PUVA therapy with psoralen in 
aqueous gel is a useful therapeutic modality for treatment of psoriasis 
patients, and patients with recalcitrant dermatoses such as palmoplantar 
psoriasis and hyperkeratotic eczema.