Prevalence of sensitive skin and its biophysical response in a Mexican population

AIM: To describe the frequency and biophysical response of sensitive skin in Mexican subjects, using the lactic acid test.

METHODS: The lactic acid stinging test was applied to 250 healthy volunteers, both sexes, 18 years of age or older, without any active dermatoses on the test site. Volunteers were university students, workers of public institutions, and general population from San Luis Potosi, Mexico. Participants were not excluded based on socioeconomic status. Demographic data were obtained through a questionnaire. Skin phototype was obtained through colorimetry. Subjects were randomized to receive 10% lactic acid on one nasolabial fold and placebo on the other side. The presence and intensity of adverse sensations, such as itching, burning, or stinging, was evaluated through a 10-point Visual Analogue Scale (VAS) prior to treatment and at 3, 5, 8 and 10 min after the intervention. Subjects with a VAS of 2 or higher were considered positive for the test. A VAS lower than 2 was considered a normal response to skin manipulation. Simultaneously, biophysical changes and barrier function were assessed by colorimetry, transepidermal water loss (TEWL), and capacitance. To decrease measurement variations by skin manipulation, the nasolabial fold was segmented in four areas of 1 cm² for each time measurement. Descriptive analyses were made using central tendency measures. Analyses of data were performed using two-tailed χ² test, Fisher’s test, t-test, logistic regression, or Mann-Whitney U test for non-parametric values between groups.

RESULTS: Of the included 246 subjects, 68% were women and the mean age was 32 years. The most frequent skin phototype was V (ranges II-V). Thirty-six percent of the subjects identified themselves as having sensitive skin. Fifty-two percent of the subjects were positive to the lactic acid stinging test, with a mean VAS of 4.5 at 3 min. Subjects with the self-diagnosis of sensitive skin were more likely to be positive for the test (80% vs 36%, P < 0.001). Lighter skin phototypes (types II and III) showed a higher response to the test compared to darker skin tones (type V; OR = 0.88, P < 0.001). There were no statistical differences in baseline biophysical measurements. At 3 min, TEWL was significantly higher in subjects positive to the test (27.5 vs 23.7, P < 0.05). At 5 min, TEWL and capacitance showed statistical differences (26.0 vs 22.4, P < 0.05, and 239 vs 179, P < 0.05, respectively). After 5 min, values tended to return to baseline levels in both groups.

CONCLUSION: Sensitive skin is frequent in our population. Darker skin phototypes have a lower prevalence of this syndrome, probably due to inherent differences in skin barrier function.