A comparative study of the effects on the skin of a classical bar soap anda syndet cleansing bar in normal use conditions and in the soap chamber test

Background/aims: The skin irritation potential of a body cleansing product is often compared under exaggerated test conditions, although the product i s intended to be used at home with repetitive and brief contact with the sk in. The aim of this study was to determine how much patch testing is predic tive of the clinical, sub-clinical and subjective cutaneous effects of prod ucts used at home by consumers for their normal hygienic cleansing. Methods: A double-blind comparative study of the normal use of an alkaline soap bar and a syndet at home during 10 consecutive weeks was performed on two identical groups of 25 healthy female subjects. The eventual skin chang es observed at different anatomical skin sites were evaluated by clinical v isual examination and by bioengineering measurements before the start of th e study and then every 2 weeks. The objective measurements were compared wi th the subject's perceptions of dryness, tightness and product irritancy du ring the testing. Results: The bioengineering measurements did not show any significant chang es on all the anatomical skin sites, except for a small increase in skin pH with the classical soap bar. However, a trend appeared, showing that the a lkaline soap bar is perceived by the subjects themselves as more of an irri tant than the syndet bar. In the soap chamber test, the bar soap showed a s ignificantly higher irritancy than the syndet bar. Conclusion: This study showed that cutaneous irritation induced by cleansin g products in patch testing is not necessarily predictive of the irritation likely to occur in normal use conditions. Finally, a clear relationship co uld be demonstrated between the results of the soap chamber test and the co nsumer perception of both cleansing bars.