Correlation between stinging, TEWL and capacitance

Background/aims: To study the correlation between stinging and skin barrier and to make the lactic acid stinging test much safer. Methods: The modified lactic acid stinging test with 3% and/or 5% aqueous solution of lactic acid combined with transepidermal water loss (TEWL) and capacitance (CAP) was used. The amount of 50 muL-test material was applied on test areas, the skin of both sides nasolabial fold of 50 healthy subjects. Subjects assessed stinging basing on a 4-point scale at 0, 2.5, 5.0 and 8 min TEWL and CAP were measured at baseline and 8 min. Results: The results show that the tendency of decrease in baseline CAP and increase in baseline TEWL are proportional with the increase of the sum of clinical scores (CSS). In 5% lactic acid test, negative correlation between changing ratio of TEWL (P-TEWL) and clinical score at 5 min (CS5 min), and negative correlation between changing ratio of capacitance (P-CAP) and CS5 min are registered. Conclusions: Our data indicate that there is certain relationship between the degree of stinging and the skin barrier. The stinging test method modified by lower concentration aqueous lactic acid and the assessment combined with P-TEWL and P-CAP is suitable for Chinese to evaluate the skin susceptibility.