Hair pull test: Evidence-based update and revision of guidelines.

Abstract

The hair pull test lacks validation and has unclear pretest guidelines. We sought to quantify normal hair pull test values and elucidate the effect of pretest hair washing and brushing. The impact of hair texture and lifestyle was also examined. Participants (n = 181) completed a questionnaire recording demographics, medications, and hair health/history. A single hair pull test (scalp vertex) was performed. The mean number of hairs removed per pull was 0.44 (SD 0.75). There was no significant difference in the mean number of hairs removed regardless of when participants washed (P = .20) or brushed (P = .25) their hair. Hair pull test values were similar between Caucasian-, Asian-, and Afro-textured hair. There was no significant difference in hair pull values between participants taking medications affecting hair loss and participants not taking these medications (P = .33). Tight hairstyles did not influence hair pull test values. Participant hair washing and brushing could not be controlled during the study, but this information was documented and analyzed. Normal values for the hair pull test should be reduced to 2 hairs or fewer (97.2% of participants). The current 5-day restriction on pretest hair washing can be reduced and brushing be made permissible.