10 Commonly Used Chemicals in Shampoos Diethanolamine (DEA) Sodium Lauryl Sulphate (SLS) Sodium Laureth Sulphate (SLES) Propylene Glycol. Benzalkonium Chloride and Benzethonium Chloride. Formaldehyde. Cocamidopropyl Betaine- (CAPB) Methylchloroisothiazolinone – MIT These hazardous chemicals are listed in the RTECS database of toxicity and even  considered a toxic waste chemical by the EPA.