Formaldehyde, a strong foul-smelling gas, found in hair smoothing products is a known cancer causing substance.

Salons and other employers, such as beauty schools, that use hair smoothing products that contain or may release formaldehyde are supposed to follow the requirements of OSHA's ‘formaldehyde and hazard communication standards’. Citations and fines were issued by OSHA to salons and other employers (e.g., beauty schools) who were found to violate norms.
Formaldehyde, a strong foul-smelling gas, is a known cancer causing substance. Hair smoothing products may contain formaldehyde dissolved in water. The chemically reacted form is called methylene glycol.
Hair smoothening products release formaldehyde when heated, viz., flat-ironing or blow-drying.
Exposure to formaldehyde can occur in the following ways:
• Breathing it in through your nose and mouth
• Getting it in your eyes or mouth
• Eye irritation and damage, including blindness.
• Nose irritation, including bloody noses.
• Skin sensitivity, rashes, and itching.
• Breathing difficulties, such as coughing and wheezing.
Formaldehyde levels above 0.1 ppm in the air can irritate nose, throat, and lungs. Higher levels worsen symptoms.
It is important that employers and employees know the risks of using formaldehyde containing products. It is not however easy since most products never list their ingredients. Products that contain formaldehyde, methylene glycol, formalin, methylene oxide, paraform, formic aldehyde, methanal, oxomethane, oxymethylene or Chemical Abstract Service Number 50-00-0 are not recommended by OSHA.
Several brand-name products that contain formaldehyde or that can expose you to formaldehyde during use have been identified:
• Acai Professional Smoothing Solution
• Professional Brazilian Blowout Solution
Cadiveu
• BrasilCacau
• Acai Therapy
Copomon/Coppola
• Keratin Complex Smoothing Therapy
• Natural Keratin Smoothing Treatment
• Natural Keratin Smoothing Treatment Blonde
• Express Blow Out
Marcia Teixeira
• Brazilian Keratin Treatment
• Advanced Brazilian Keratin Treatment
• Chocolate Extreme De-Frizzing Treatment
• Soft Gentle Smoothing Treatment
• Soft Chocolate Gentle Smoothing Treatment
Reference: Facts about Formaldehyde in Hair Smoothing Products; Occupational Safety & Health Administration.
Source-Medindia