Assessment of the photoprotection properties of hair cosmetics using the hemispherical directional reflectance method.

BACKGROUND: Solar radiation is responsible for changes in the structure of human hair, the damages include proteins (65%-95%), lipids, and melanin. The aim was to examine the effectiveness of sunscreen in hair cosmetics and whether hair color affects it. MATERIALS AND METHODS: The study included nine women, divided according to hair color to three groups: light, dark, and gray hair. The 410-Solar reflectometer was used in five time points. The hair was divided into three strands, one product applied to each. RESULTS: Dark hair showed the highest absorption of radiation in all wavelength ranges, the reflectance before products application was significantly higher than the hair reflectance immediately after application. The effect of sunscreens on light hair reflectance was found at wavelengths 400 and 720 nm and between 1000 and 2500 nm, the reflectance before application was significantly higher than the reflectance after. The use of products on gray hair did not have a significant effect on hair reflectance at wavelengths 400-1100 nm, the effect of sunscreens on the gray hair reflectance was observed in the UV and infrared range, the reflectance before application was significantly higher than immediately after. CONCLUSIONS: The results showed that the 410-Solar reflectometer is useful to assess the effectiveness of hair sunscreens. All three tested hair products do not show the expected protection properties. Dark hair showed the highest absorption of radiation in all wavelength ranges, suggesting that dark hair should be more protected against radiation than light and gray hair.