The British journal of dermatology
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This study assesses the variability of two non-invasive methods of measuring stratum corneum barrier function in vivo. Transepidermal water loss (TEWL), and the vascular response to hexyl nicotinate (HN) penetration as determined by laser-Doppler flowmetry, were measured in a group of 21 healthy volunteers. Each time profile of the vascular response to HN penetration was analysed using the following parameters: the baseline cutaneous blood flow, the lag-time between application and initial response (t0), the time between application and maximum response (tmax), the maximum response, and the slope of the curve. ⋯ The intra-individual reproducibility of t0 and tmax. for HN penetration was also high (relative differences of 2.8 and 3.1%, respectively). The other vascular response parameters were less reproducible (relative differences of 6.9-18.6%). We conclude that TEWL and selected parameters of HN penetration, as non-invasive tests of the stratum corneum barrier function, yield reproducible results and are hence useful for investigations assessing the skin barrier function in various disorders.
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In the U. K., PUVA treatment for psoriasis is usually given three times weekly, with the starting dose of UVA chosen according to the skin type of the patient. Observations on the time-course and dose-response characteristics of PUVA erythema suggest that larger doses of UVA could be used safely, provided that the frequency of PUVA treatment is reduced. ⋯ These results compare favourably with previous studies in which treatment was given three or four times weekly. Thus, twice weekly PUVA treatment for psoriasis is at least as effective as treatment given more frequently, and may be safer, as lower cumulative UVA doses are required for clearance. It also allows for more efficient operation of a PUVA unit and is more convenient for patients.