10 Ways Chemical Treatments Damage Your Hair


2. Formaldehyde damage

Formaldehyde is essential to many hair treatments and has been successfully used to straighten hair, but it should be used with care.  Formaldehyde is a known carcinogen, so exposure should be kept as low as possible; use it only in a place with adequate ventilation.  Keratin treatments using formaldehyde tend to also use heat, and when both are excessive, chemical burn of hair or scalp may result.