J. Cosmet. Sci., 62, 579–585 (November/December 2011) 579 Hair breakage by combing and brushing—A comment on: T. A. Evans and K. Park, A statistical analysis of hair breakage. II. Repeated grooming experiments, J. Cosmet. Sci., 41, 439–456 (2010) Y. K. KAMATH and C. ROBBINS, Kamath Consulting Inc., 11 Deer Park Drive, Monmouth Junction, NJ 08852 (Y.K.K.), and 12425 Lake Ridge Circle, Clermont, FL 34711 (C.R.). Accepted for publication June 9, 2011. Synopsis Literature dealing with the mechanisms of hair breakage in combing and brushing published so far has been reviewed as a background for the critical evaluation of the method and data analysis of the paper “Statistical Analysis of Hair Breakage. II” by Evans and Park (1). Accumulated knowledge about hair breakage in these grooming processes indicates that hair breakage in combing and brushing results from tangling, looping, knotting, and impact loading. Fatiguing, though responsible for some weakening of the fi ber in the grooming process, it is unlikely to be a signifi cant factor in hair breakage in combing and brushing. INTRODUCTION Hair breakage is a complex multifactorial phenomenon involving: Tangle formation with hair fi bers looped over other hairs and severe bending deformations • (2) Impact breakage (3) or pulling a comb or brush through a tangle with breakage • Knots (4) that form more with high curvature and are easily fractured • Treatments and weathering (5–10): Chemical damage increases breakage and • conditioners decrease breakage Relative humidity or water content of the hair (10,11): Highly coiled hair breaks • more by dry state grooming (10) while straight-to-wavy hair provides more short segment breaks ( 2.5 cm) when dry (10), but more long segment breaks when wet (10) Physical damage or wear by abrasion (1,3,10,12) from specifi c grooming devices such • as combs, picks or brushes, and to some extent a fatiguing action