Salt water bathing prior to UVB irradiation leads to a decrease of the minimal erythema dose and an increased erythema index without affecting skin pigmentation

The combination of salt water baths and solar radiation is known as an effe ctive treatment for patients with psoriasis and atopic dermatitis, To deter mine whether increased susceptibility to UVB radiation may contribute to th is therapeutic effect we have studied the effect of bathing the skin in sal t water prior to UVB irradiation. Twelve subjects were phototested on the v olar aspects of their forearms with increasing doses of WE radiation, One f orearm was exposed to 5% salt water prior to irradiation. The minimal eryth ema dose (MED) was determined and the erythema index and skin pigmentation were assessed by photometric measurement. The combination of salt water bat h and irradiation yielded a significant decrease of the MED when compared t o WE alone (median 90 mJ/cm(2) vs 130 mJ/cm(2), P < 0.01). Analysis of vari ance showed a significant influence of salt water bath on erythema (P < 0.0 5) but not on skin pigmentation, Within the MED test area the erythema inde x of the salt water exposed forearms was elevated significantly (P < 0.05) while skin pigmentation was not affected, Thus, bathing the skin in salt wa ter leads to a decreased threshold level for the elicitation of UVB-induced erythema and a selective increase of the erythemal response. This sensitiz ation to the effects of shortwave UVB radiation may increase immunosuppress ive effects of UVB radiation and may lead to an increased efficacy of UVB p hototherapy. However, there is also an increased sunburn risk when salt wat er baths are followed by exposure to UV radiation.