Skin irritation from air-oxidized ethoxylated surfactants

Area of Science:

• Dermatology
• Cosmetic Science
• Toxicology

Background:

• Surfactants are widely used in cosmetics but can be skin irritants.
• The impact of chemical changes, like oxidation, on surfactant irritancy is not well understood.
• Non-ionic ethoxylated alcohols (e.g., C12E5) are common in skincare due to their mildness.

Purpose of the Study:

• To investigate how oxidation affects the skin irritant potential of a non-ionic ethoxylated alcohol, C12E5.
• To compare the irritancy of pure C12E5 with its oxidized form.
• To assess irritancy under single and repeated exposure conditions.

Main Methods:

• Patch testing on 18 healthy volunteers using pure and oxidized C12E5.
• Two protocols: single 24-hour exposure and repeated exposures.
• Irritation assessment via visual scoring, transepidermal water loss (TEWL), and skin blood flow measurement.

Main Results:

• No significant difference in irritation between pure and oxidized C12E5 after single exposure.
• Oxidized C12E5 showed significantly higher irritancy than pure C12E5 after repeated exposures at 9% and 27% concentrations (p<0.05).
• Visual scoring and instrumental measurements (TEWL, blood flow) supported these findings.

Conclusions:

• Oxidation significantly enhances the skin irritant potential of C12E5, particularly with prolonged or repeated contact.
• The findings suggest that changes in surfactant composition during storage or handling can alter their safety profile.
• This is important for the formulation and safe use of skincare products containing ethoxylated surfactants.