Alternative Protocol for Hair Damage Assessment and Comparison of Hair Care Treatments

AIM: The aim of this study is to propose a new quantification protocol for determining the change in hair properties on weathering and formulate hair damage protection metric to compare different hair care products. SUBJECTS AND METHODS: The study was conducted with 30 participants (nonhair oil users), wherein hair samples were collected and evaluated for (a) average cross-section and mean diameter at different sections of strand and (b) breakage point location on hair extension. Correlation between breakage point and hair mean diameter as function of length was studied. Inferences were extrapolated to characterize the quality of hair samples in (a) another matched group of 30 participants (coconut oil users) and (b) studies on hair swatches with different hair treatments. RESULTS: In accordance with the weakest link theory, on extension hair fractured at the section where average mean diameter (or cross section) is the smallest (correlation R(2) = 0.86). The weakest link in hair fiber is connected with irregularity in hair strands-characterized by root mean square variability (Rq). We found that tips of hair have ~100% more Rq than the roots. Furthermore, regular coconut oil users have hairs with Rq lower by ~65% in comparison to nonoilers. Hair swatch studies confirmed that coconut oil-wash cycles (n = 20) help reduce Rq by 30%, whereas other hair treatments such as shampoos and conditioners did not lead to much change. A new metric was proposed – hair protection factor – to quantify damage control power of various products. CONCLUSIONS: Hair breakage is a complex phenomenon with multi-factorial effects. The present work identifies irregularities in mean diameter along hair length as the precursor for hair strength. The weakest link in hair is characterized by the presence of internal defects-preceded by surface irregularities. From root to the tip, cuticle chip-off increases and so does the Rq and tendency to break. Thus, the metric based on Rq can help compare hair care treatments in their promise to control hair damage.