Influence of antioxidants on the sun protection properties of hair care products.

ABSTRACT

Aim of this study was to determine the influence of commercially available antioxidants on sun protection properties of hair care products. To evaluate changes of human hair L*a*b-color measurements, tensile strength measurements and high pressure dynamic scanning calorimetry (HPDSC) measurements were carried out. To have a measure for the concentration of the activity of the reactive species, causing hair or color damage, chemiluminescence measurements were carried out. Before the test with the antioxidants experiments were carried out to evaluate effects of varied artificial weathering conditions on physical properties of hair. Here high relative humidity (85%) and low radiant flux (600W/m2) exhibited the biggest changes in natural hair color but the lowest changes in the in tensile strength and HPDSC measurements. All of the tested antioxidants reduced the chemiluminescence level when used in a pre-sun or after-sun formulation. According to the HPDSC measurements the antioxidants showed a slight increase of the peak temperature and therewith a hint towards a protection effect when used in a pre-sun or after-sun product. In contrast thereto some of the antioxidants reduced the tensile strength of sun care products for hair when added. A slight reduction in the lightening of natural hair color could be observed when antioxidants were present in the sun care formulations. The effect of antioxidants in sun care formulations used on dyed hair was strongly dependent on the shade of hair. The addition of some antioxidants yielded significant improvements of the protection properties of the used sun care product in some measurement methods.