Effect of ethnicity, gender and age on the amount and composition of residual skin surface components derived from sebum, sweat and epidermal lipids

Abstract

Background/purpose: The superficial layer on the skin surface, known as the acid mantle, comprises a mixture of sebum, sweat, corneocyte debris and constituents of natural moisturizing factor. Thus, the phrase 'residual skin surface components' (RSSC) is an appropriate term for the mixture of substances recovered from the skin surface. There is no general agreement about the effects of ethnicity, gender and age on RSSC. The aim of this human volunteer study was to evaluate RSSC in relation to ethnicity, gender and age. A suitable acquisition medium for RSSC collection was identified and samples of RSSC were subsequently analysed using gas chromatography-mass spectrometry (GC-MS) and gravimetry.

Methods: A total of 315 volunteers participated in the study from a range of self-declared ethnic backgrounds. Six acquisition media were compared to determine the most suitable media for RSSC collection. The effect of age, gender and ethnicity on RSSC collection was evaluated by gravimetric analysis while GC-MS was used to determine the composition of RSSC.

Results: Of the six candidate materials assessed, cigarette paper provided the most practical and reproducible sample acquisition medium. There was no significant difference in the amount of RSSC collected when based on gender and ethnicity and no significant correlation between RSSC recovery and age. Up to 49 compounds were detected from human RSSC when analysed by GC-MS.

Conclusions: The results of the present study suggest that RSSC can be effectively collected using cigarette paper and analysed by GC-MS. Ethnicity, gender and age had no significant impact on the quantity of RSSC recovered from the skin surface.

Keywords: age; cigarette paper; ethnicity; gas chromatography-mass spectrometry; gender; sebum; skin surface lipids.

Figure 1

Representative light microscope images of polyurethane (PU) foam A and B. The average pore size of type A and type B foams were 300 and 75 µm, respectively.

Figure 2

Demographic presentation of self-declared ethnic groups based on age and gender. The x-axis refers to the number of males or females expressed as function of age (y-axis) according to self-declared ethnicities (African, White and Asian).

Figure 3

Amount of residual skin surface components (RSSC) collected (n = 5 replicates) from one volunteer (Volunteer A: African, female, 26 years old) using six collection media. Each box represents interquartile range with median, while minimum and maximum values of RSSC collection are shown by bars. The number above each boxplot denotes the coefficient of variation (CV) of RSSC collection among three volunteers (Volunteer B: Asian, male, 29 years old; Volunteer C: African, female, 34 years old).

Figure 4

Reproducibility of residual skin surface components (RSSC) collected on two different occasions from 10 randomly selected volunteers. No statistically significant difference was observed in RSSC accumulation on two different occasions (paired t-test, P > 0.05).

Figure 5

Residual skin surface components (RSSC) collection from 161 males and 154 females after 1 h. No change in RSSC accumulation with increasing age was observed for either gender.

Figure 6

Components of residual skin surface components (RSSC) identified by GC-MS analysis. Detected compounds were classified into five groups: free fatty acids, cholesterol and cholesterol esters, squalene, wax esters and triglycerides.