Research Summary
Skin disorders are often treated with creams containing various active substances. These creams also contain emulsifiers, which are surface-active ingredients used to stabilize the emulsion. Emulsifiers are potential irritants, and in the present study, the influence of stearic acid, glyceryl stearate, PEG-2, -9, -40, and -100 stearate, steareth-2, -10, and -21 on normal as well as irritated skin has been evaluated using non-invasive measurements.
Test emulsions were created by incorporating 5% emulsifiers in a water/mineral oil mixture (50:50). The emulsions and their vehicle were then applied to normal skin for 48 hours and to sodium lauryl sulfate (SLS)-damaged skin for 17 hours in aluminum chambers. Twenty-four hours after removal of the chambers, the test sites were evaluated for the degree of irritation.
In normal skin, the emulsifiers induced significant differences in transepidermal water loss (TEWL) but not in skin blood flow. Five of the emulsifiers increased TEWL. In SLS-damaged skin, an aggravation of the irritation was expected; however, no differences regarding skin blood flow were noted from the emulsifiers. Furthermore, three emulsifiers unexpectedly decreased TEWL.
These results highlight the possibility of absorption of these emulsifiers into the lipid bilayer, which increases TEWL in normal skin and decreases TEWL in damaged skin.
Keywords: Surface-active agents, Nonionic emulsifiers, Normal skin, Surfactant-irritated skin, Barrier function.
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