[Shower PUVA: a new possibility for topical PUVA therapy. Phototoxicity in relation to shower time, water temperature and skin type].

During the past few years, bath PUVA has become established as an effective treatment for various dermatoses and especially for psoriasis. Using 3,4,5 trimethylpsoralen (TMP) in combination with subsequent UVA irradiation, a shower PUVA has been developed as an alternative in local PUVA therapy. This involves moistening the patient's skin - with the exception of the head and neck area - in a shower using water containing psoralen (TMP concentration 0,27 mg/l). The advantages of shower PUVA method are that time, space and cost savings are possible and that only a slight amount of physical exertion is required by the patient standing in the shower compared to immersing the whole body during bath PUVA therapy. The efficacy and practicability of shower PUVA were evaluated using the minimal phototoxic dose (MPD) for healthy volunteers assessing water temperature (33-38 degrees C), shower time (5-10 min), and UVA dose (0,06-1,0 J/cm(2)). Additionally, the time course of TMP-induced photosensitivity was observed over a period of 4 hours after the shower. Using a TMP concentration of 0,27 mg/l, the MPD for skin type I-II lay between 0,125-0,375 J/cm(2) and for skin type III-IV between 0,375-1,0 J/cm(2). Photosensitivity was induced by shower PUVA within 5-10 minutes shower time and at 33-38 degrees C water temperature. MPD exhibited an inverse correlation to temperature but no differences were apparent for shower times between 5 and 10 minutes. Photosensitivity completely disappeared within 2 hours. Minimal phototoxic doses using TMP in shower PUVA are comparable with classical bath PUVA when taking skin type into account. These results support the therapeutic use of shower PUVA using TMP.