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Study of the cytotoxic and irritant effects of skin cleansing soaps.

Background
The use of soap for skin cleansing is common among the population. However, it is possible that it causes damage to skin cells and disrupts the skin barrier.


Objective
To determine the cytotoxic effect of soaps on in vitro-cultured keratinocytes and to correlate it with clinical irritation.


Method
A survey was conducted to find out the most widely used commercial soaps and their number. Subsequently, their cytotoxicity was evaluated in human keratinocyte cultures using the resazurin assay. The soaps with the highest and lowest cytotoxicity were applied to the skin of healthy volunteers to assess their effect on the skin barrier using colorimetry and transepidermal water loss (TEWL) assays.


Results
Of the analyzed soaps, 37 % were shown to be toxic to keratinocytes in vitro. The soap with the highest toxicity induced the highest rate of erythema and TEWL, in comparison with the least toxic soap and the vehicle used as the control solution.


Conclusion
Soaps marketed for skin cleansing can contain chemical ingredients that damage human keratinocytes and cause skin barrier subclinical irritation. Their use can worsen preexisting dermatoses, generate xerotic or irritant contact dermatitis, and cause atrophy and dermatoporosis.