Chemical damage occurs when you’ve overprocessed your hair, which can happen both at home and in salons. “When you overuse home color (i.e. dye it too often) or leave it on for too long, it can be very aggressive on your hair,” warns Picciano. “Or, in the salon, if your stylist pushes your hair past its breaking point (usually by overlapping areas of bleach), that will cause breakage as well.”
And it’s not just hair color that causes your hair to become brittle, it could also be chemicals that are used in different perms or relaxers. “When any of these processes are done, the hair’s disulfide bonds are broken down, which is detrimental because these bonds count for one third of the hair’s strength,” explains Gretchen Friese, a certified trichologist for BosleyMD.
Chemical damage on its own would be enough to dry out your hair, but when you pair that with “constant heat exposure and thermal styling, it can weaken the hair significantly, causing it to feel brittle and break,” says Aura Friedman, a celebrity colorist at Sally Hershberger salons.