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

<bold>Background: </bold>The hair pull test lacks validation and has unclear pretest guidelines.<bold>Objective: </bold>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.<bold>Methods: </bold>Participants (n = 181) completed a questionnaire recording demographics, medications, and hair health/history. A single hair pull test (scalp vertex) was performed.<bold>Results: </bold>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.<bold>Limitations: </bold>Participant hair washing and brushing could not be controlled during the study, but this information was documented and analyzed.<bold>Conclusion: </bold>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. [ABSTRACT FROM AUTHOR]