A curly hair can also be described according to its composition and structure. A research team based in Clichy, France, and working for the cosmetics firm L’Oréal, used electron microscopy to compare straight and curly hair fibers. The former were circular in cross section and symmetrical in structure. The latter, though, had an uneven distribution of a particular type of keratin. This protein—which, along with other varieties of keratin, serves as the primary component of hair—accumulated near the inside edge of a curled hair, beneath the curve. Even if you’re born with symmetrical follicles, there are some ways in which straight hair can turn curly. Scientists have found that a cellular receptor called EGFR clusters on the outer root sheath of a follicle and appears to regulate the growth of hair. Certain cancer drugs that inhibit these receptors may cause a patient to develop curly hair as a side effect. Have a burning science question you’d like to see answered in our FYI section? Email it to fyi@popsci.com.
