52 FORMULATING FOR MILDNESS Area ratio
Skin surface SC
~20µm deep
CD/CH 3.5 a.u
Skin surface SC
~20µm deep
Total depth in skin 60µm
0 a.u
Figure 6: Confocal Raman image analysis of water content: Untreated, control skin.
penetration test used surgical human abdominal skin (ex vivo) as the medium. In addition to evaluating the Polyglyceryl-10 caprylate/caprate mild surfactant, Lonza evaluated sodium dodecyl sulfate (SDS), recognised as a positive skin irritant. Samples of Polyglyceryl-10
caprylate/caprate + SDS surfactants, and SDS alone were each applied to the ex vivo skin medium and measured via a WITec Alpha 300R Plus Confocal Raman Microscope. Scientists measured the penetration of SDS into the stratum corneum - the outer layer of the skin, 20 microns beneath the skin surface - and the presence of water in the stratum corneum. The images were processed with WITec Project Plus software.
Skin applied with SDS alone had significant SDS penetration into the stratum corneum (Fig 4). High surfactant penetration can compromise the surface of the skin and cause disruptions to the stratum corneum. Figure 5 shows skin applied with a surfactant combination of Polyglyceryl-10 caprylate/caprate mild surfactant and SDS. Surfactant presence is limited to the skin
Total depth in skin 60µm
Figure 7: Confocal Raman image analysis of water content: SDS-applied skin.
surface, mitigating the penetration of SDS into the stratum corneum.
The Polyglyceryl-10 caprylate/caprate mild surfactant thus protects the surface of the skin and the stratum corneum from potential damage caused by some harsh surfactants. Traditional surfactants have the potential not only to damage the stratum corneum, but disrupt the delicate balance of water and potentially create issues with how the skin functions. The effects of surfactant penetration can be shown by measuring the amount of moisture in and below the stratum corneum. Figure 6 shows the presence of water in
untreated healthy skin, the control for the water content analysis. Red, yellow and orange indicate higher concentrations of water in the skin. Purple indicates low water content, and the dotted line represents the skin surface. In general, there is less water content nearer to the surface because more moisture evaporates from the surface. Skin applied with SDS alone had higher concentrations of water near the surface (Fig 7). As noted, SDS disrupts the water content in the stratum corneum – shown by
Skin surface SC
~20µm deep
the concentration of bright red, yellow and orange on the skin — and has the potential to cause damage to the stratum corneum. Skin applied with Polyglyceryl-10 caprylate/caprate and SDS surfactants matched the control (Fig 8). Much of the water content exists below the surface of the skin and stratum corneum. This result shows the balance of water in the skin is not as affected by SDS when the skin is is in contact with Polyglyceryl-10 caprylate/caprate mild surfactant. Thus Polyglyceryl-10 caprylate/caprate mild surfactant can help maintain the stratum corneum moisture balance, and protect the skin from potential damage caused by harsh surfactants.
Conclusion
Polyaldo 10-1-CC mild surfactant delivers the best of both worlds. It offers an excellent irritation profile, with mildness on a par with PEG-80 sorbitan laurate, combined with the initial flash foaming speed of decyl glucoside, a moderate to severe irritant (based on our study). Polyaldo 10-1-CC mild surfactant builds foam structure faster than PEG-80 sorbitan laurate, and creates a more stable foam structure and creamier foam. It has higher surface activity than PEG-80 sorbitan laurate, resulting in efficacious cleansing and a better cost-performance ratio. Classified as very low-irritating, it is a gentle surfactant for skin and hair applications where mildness is needed. In addition, Polyaldo 10-1-CC mild surfactant mitigates surfactant penetration into the stratum corneum, protecting skin from potential damage caused by harsh surfactants and maintaining the stratum corneum moisture balance.
Total depth in skin 60µm
Figure 8: Confocal Raman image analysis of water content: skin applied with Polyaldo 10-1-CC mild surfactant + SDS.
PERSONAL CARE EUROPE
Reference 1 Jane Jang, Senior Beauty Analyst at Mintel, From “A Bright Future: South Korea Ranks Among the Top 10 Beauty markets globally, Mintel. Published April 4, 2017. Accessed July 5.
PC April 2018
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