Two dermatologists went through the published research on traction alopecia and pulled it together into one review. Traction alopecia is hair loss caused by sustained pulling on the follicle, the small pocket in the skin that each hair grows out of. The styles the review associates with higher risk are the ones that hold tension on the hair for long stretches: tight buns and ponytails, weaves and extensions, tight braids including cornrows and locs, and tightly worn turbans and head coverings. The review also flags that chemically relaxing the hair and then wearing it in a high-tension style carries more risk than either one on its own.

The review gathers its numbers from separate studies rather than running its own. Across the research it cites, roughly a third of women of African descent are affected, with individual clinic and community studies landing anywhere from 1 percent to 37 percent depending on which population was looked at. One South African school study found traction alopecia in 8.6 percent of first-year girls and 21.7 percent of final-year girls. The earliest visible sign the authors describe is perifollicular erythema, meaning redness in the skin right around the follicle openings, and they write that most cases can be reversed when the tension comes off early enough. The authors also state plainly that prevalence data across the general population is thin and likely undercounted, partly because these styles are common and the early changes often go unremarked.

Here's the study: Billero V, Miteva M. Traction alopecia: the root of the problem. Clinical, Cosmetic and Investigational Dermatology, 2018. Read it here

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