What really is normal?
The Hair Pull Test: 3 is abnormal
Telogen effluvium is a form of hair loss where patients experience increased daily hair shedding. Instead of losing 40 or 50 hairs per day, patients with “TE” lose 80 to up to 600 hairs per day. A ‘pull test’ has traditionally been one of the methods that hair specialists are taught to perform when examining the scalp. To perform the test, 60 hairs are lightly grasped between the thumb and index finger and gently pulled upwards. Removal of more than 10 % of the hairs in the bundle (i.e more than 6 hairs) has been traditionally viewed as a positive pull test.
McDonald and colleagues from Ottawa, Canada performed a study revisiting this issues of what exactly constitutes a normal pull test and what limits should be set for abnormal. They studied 181 otherwise healthy individuals. The authors showed that for the vast majority of individuals, a pull test of 60 hairs extracts 0,1 or 2 hairs (97 % or more have 2 or less). The average was 0.44 hairs indicating that many individuals have no hairs removed. Interestingly, the date the patient last washed their hair, did not influence the pull test result nor did the frequency of brushing the hair.
This is one of my favourite studies of the year. It is simple and elegant and answers a lot important questions. I have long abandoned the “6 hair rule” for the pull test, and frequently have told the dermatology residents and trainees that work with me that even a few hairs coming out is abnormal. I’m grateful for this well conducted study and it has renewed my interest in the pull test.
McDonald et al. Hair pull test: Evidence-based update and revision of guidelines. Journal of the American Academy of Dermatology 2017; 76: 472
Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887