Keratin Treatments – Used increasingly over the last 10 years, these are salon-offered treatments that are performed on loosely curled, wavy, or straight hair. They contain formaldehyde and are used to provide a straight pattern to the hair shaft which results in a smoother hairstyle with blow-drying the hair. Health Canada has identified several salon-based keratin treatment products that contain excess formaldehyde. Formaldehyde is permitted in levels of 0.2% or lower in cosmetics, and is a preservative in several products. It has been cautioned that formaldehyde is a sensitizer that can vaporize when heat is applied to the hair (e.g. blow drying and ceramic straightening). The adverse effects associated with these treatments include burning of mucus membranes (eyes, nose, and throat), breathing difficulties, and even hair loss
Information as per the Canadian Dermatology Association https://dermatology.ca/public-patients/hair/hair-care/
