Efficacy of skin barrier creams (III). The repetitive irritation test (RIT) in humans.

2 barrier creams (BC) were evaluated against the anionic detergent sodium lauryl sulphate (SLS) using a new human test model. In the repetitive irritation test (RIT) on human skin, the irritant SLS is applied to the ventral forearm of healthy volunteers daily for 2 weeks. 1%, 5%, and 10% SLS is exposed to the skin for 30 min, using a glass cup 2.5 cm in diameter. The BC is applied 30 min before the irritant. Cutaneous irritation is assessed on a score for erythema (0 to 5+), and quantified by various biophysical techniques: transepidermal water loss (TEWL) by evaporimetry, skin blood flow volume (BFV) by laser-Doppler velocimetry, and skin colour by colorimetry (La* value). 10 subjects were tested with SLS on one forearm without pretreatment (control) and with Taktosan Salbe as BC on the other forearm. A 2nd panel of 10 subjects was tested in the same way with SLS and Marly skin as BC. Taktosan Salbe was extremely effective in reducing the irritation by SLS: there were significant differences regarding all test parameters for 10% SLS in the 2nd week. The most differentiating parameter was TEWL, revealing statistical differences as early as the 1st week for 10% SLS and Taktosan Salbe, while the least differentiating sensitivity was found for La*. In contrast, there was no significant suppression of irritancy in any parameter with Marly skin, either in the 1st week or in the 2nd week with any concentration of SLS.(ABSTRACT TRUNCATED AT 250 WORDS)