Chemically treated hair refers to hair that has undergone processes like coloring, perming, or straightening, which can weaken the hair shaft and lead to damage. These treatments can strip hair of its natural moisture, leaving it dry, brittle, and prone to breakage. Maintaining chemically treated hair requires special care, including using sulfate-free shampoos, deep conditioning treatments, and minimizing heat styling. Regular trims and protective styles can also help preserve hair health and prevent further damage.