By Dr. Liji Thomas, MD Reviewed by Lauren Hardaker Feb 16 2026 A first-of-its-kind chemical analysis reveals that many widely used hair extensions contain hazard-listed substances, highlighting gaps in labeling and oversight while underscoring that the presence of chemicals does not necessarily mean proven health harm. Study: I dentifying Chemicals of Health Concern in Hair Extensions Using Suspect Screening and Nontargeted Analysis . Image credit: Vershinin89/Shutterstock.com Hair extensions