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Effects of soap and detergents on skin surface pH, stratum corneum hydration and fat content in infants
1Department of Pediatrics, University of Vienna, School of Medicine, Austria.
Insights
Infant skin cleansing with alkaline soap significantly increases skin pH and decreases fat content more than mild detergents or tap water. These changes can disrupt the skin's protective acid mantle, potentially affecting hydration and bacterial flora.
Area of Science:
- Dermatology and Pediatrics
- Infant Skin Physiology
- Cosmetic Science
Background:
- The impact of skin cleansing products on adult skin pH, fat content, and hydration is well-established.
- Limited research exists on these effects in newborn and infant skin.
Purpose of the Study:
- To investigate whether cleansing preparations affect infant skin pH, fat content, and hydration similarly to adults.
- To compare the effects of tap water, liquid detergent, compact detergent, and alkaline soap on infant skin parameters.
Main Methods:
- An open, controlled, randomized study involving infants aged 2 weeks to 16 months without skin disease.
- Ten infants per group were assigned to cleansing with tap water (control), liquid detergent (pH 5.5), compact detergent (pH 5.5), or alkaline soap (pH 9.5).
- Skin pH, fat content, and hydration were measured before and 10 minutes post-cleansing, with statistical analysis using parametric covariance analysis.
Main Results:
- All cleansing agents increased skin pH; alkaline soap caused the largest increase (+0.45), while tap water caused the smallest (+0.19).
- Alkaline soap significantly increased skin pH and decreased fat content more than liquid or compact detergents.
- No significant differences in skin hydration were observed before and after washing across all groups.
Conclusions:
- Even tap water alters infant skin surface properties, increasing pH and potentially disrupting the protective acid mantle.
- Alkaline soap significantly impacts infant skin by raising pH and reducing fat content, which may lead to dryness and alter the skin's natural barrier function.
- Changes in skin pH and fat content can affect the cutaneous bacterial flora and epidermal enzyme activity, highlighting the importance of gentle cleansing for infants.
Background:
In adults the influence of cleansing preparations on the pH, fat content and hydration of the skin is well documented. Studies in newborn and small infants have not been reported.
Objective:
Our study aimed at examining whether similar effects can be ascertained in infants.
Methods:
Infants without skin disease, aged 2 weeks to 16 months, entered an open, controlled and randomized study. Ten infants each had skin washed with tap water (control group), liquid detergent (pH 5.5), compact detergent (pH 5.5) or alkaline soap (pH 9.5). The pH, fat content and hydration were measured before and 10 min after cleansing. Findings were statistically evaluated by parametric covariance analysis.
Results:
The skin pH increased from an average of 6.60 after cleansing in all groups. The smallest increase (+0.19) was observed in the control group, the largest (+0.45) after washing with alkaline soap. After treatment with liquid or compact detergent, the increase of the pH was only 0.09 higher than for the control group. In comparison to the compact and liquid detergents, the alkaline soap group had a significantly higher increase in pH. The fat content (mean starting value: 4.34 micrograms/cm2) decreased after washing in all groups; the smallest effect was observed in the control group (decrease of 0.93 micrograms/cm2), the highest for the alkaline soap group (decrease of 4.81 micrograms/cm2). In comparison to the compact and liquid detergents, the alkaline soap group had a higher decrease in fat content. This difference was significant for compact detergents. No statistically significant differences were observed for hydration before versus after washing.
Conclusion:
Each cleansing agent, even normal tap water, influences the skin surface. The increase of the skin pH irritates the physiological protective 'acid mantle', changes the composition of the cutaneous bacterial flora and the activity of enzymes in the upper epidermis, which have an acid pH optimum. The dissolution of fat from the skin surface may influence the hydration status leading to a dry and squamous skin.