The alkaline pH‐adapted skin barrier is disrupted severely by SLS‐induced irritation

Abstract

The pH of the healthy skin is 5.5 and maintained by many regulatory mechanisms. The pH of the skin care product we use on a daily basis can have an influence on the skin properties. To investigate how the physical properties of skin change after the alkaline or acidic pH of the skin care products are applied on the skin for a long term, we adjusted the pH of the skin care products to 3, 5 and 8 (A, B, C), with glycolic acid and triethanolamine. For 5 weeks the skin care products were applied on 20 healthy subjects' ventral forearm and the skin physical properties were measured. After 5 weeks, skin responses to the external stress of 1% (w/v) SLS (sodium lauryl sulphate) irritation and erythema by UV were measured. Skin colour and skin UV response were not altered by the pH. However, on the C-applied site (pH 8) the transepidermal water loss of stratum corneum (SC) increased significantly, the water content increased and desquamation decreased, respectively, and the SLS significantly impaired the skin barrier in comparison with other sites. The alkaline skin care product impaired the skin barrier after repeated application over 5-week period and the skin barrier was disrupted severely by 1% SLS exposure because SC was already impaired by alkaline pH and sensitive to external stress. This suggests that the pH of daily skin care products is very important for skin barrier homeostasis.

A Long-Term Study to Evaluate Acidic Skin Care Treatment in Nursing Home Residents: Impact on Epidermal Barrier Function and Microflora in Aged Skin

“…In a randomized, controlled, double-blind study, 2 groups of aged residents were nursed over 7 weeks -taking the age-related decelerated epidermal turnover time into account -with skin care products adjusted to a pH of 4.0 (group A) or a pH of 6.0 (group B). In contrast to Kim et al [49] , we discovered that skin hydration was significantly improved by application of the acidic products (p = 0.005) but not by treatment with cosmetics Table 3. Skin flora results before (baseline) and after treatment in relation to the study group adjusted to a pH of 6.0 (p = 0.161).…”

Clinical, biophysical and immunohistochemical analysis of skin reactions to acute skin barrier disruption - a comparative trial between participants with sensitive skin and those with nonsensitive skin

“…Biophysical parameters in our study did not reflect differences between participants with SS and NSS, and did not parallel the conclusion with regard to the skin barrier. Slightly lower baseline SC hydration values were found, which reached statistical significance in one study, but higher baseline values have been reported . TEWL at baseline is mainly shown to be higher in those with SS, but rarely reaches significance …”

A study on seasonal variation of skin parameters in Korean males

“…The skin pH may be affected by internal factors such as sebum, hydration, and anatomical regions and external factors such as environments and habits of using detergents and cosmetics in everyday life [15]. The skin sebum content neutralizes alkali and prevents dry skin to act as an important factor in controlling skin moisture contents [15,16]. In the results of this study, there was a significantly higher sebum secretion in measured regions, the centre of the forehead, and the glabella in summer than in winter.…”