Ask the doctor: Is hair straightening safe?

Q. I had my hair straightened six months ago. Is there any danger in getting these treatments twice a year? I hear they may contain formalin or formaldehyde.

A.Like permanent wave solutions, hair straightening products are designed to break and reform the chemical bonds in keratin, the key structural protein in hair and nails. Permanent wave solutions make the hair more curly; hair straighteners, as the name implies, make it very straight.

Several products popularized in Brazil and Japan have come into widespread use for hair straightening. Also known as hair relaxers, keratin treatments, and hair smoothing products, they are generally applied in a salon and are usually not available directly to consumers. After a prolonged application, the hair is blown dry or ironed. The process can take two to three hours and cost $300 or more. One treatment lasts two to three months. Newly straightened hair is not supposed to be washed, pulled back in a band, or put up with clips for 72 hours.

Safety is an issue because many of these products contain formaldehyde (also known as formalin), a substance that is associated with various health problems. The danger is greatest for salon workers: chronic exposure to formaldehyde increases the risk of developing cancer. Customers may also have adverse reactions to the chemical, including rashes, acute respiratory irritation, and formaldehyde sensitivity (a lifelong allergic reaction to the low and generally accepted levels of formaldehyde that are in many common products).

Respiratory problems arise because formaldehyde is released into the air during both the application of the hair straightener and the drying-and-ironing process that follows. State and local health departments have received reports of breathing difficulties, heaviness in the chest, sore throats, headache, fatigue, and burning eyes, nose, and throat.

In December 2010, Health Canada issued an advisory listing 10 hair-straightening solutions that contain concentrations of formaldehyde ranging from 1.4% to 7% — well above the allowable limit of 0.2%. Some of these products also misrepresent their content. In 2010, for example, Oregon's Occupational Safety and Health Administration (OSHA) found that samples of Brazilian Blowout Acai Professional Smoothing Solution, advertised as "formaldehyde-free," actually contained 6.8% to 11.8% formaldehyde.

Many agencies, including Health Canada, Oregon's OSHA, and the Connecticut Department of Public Health have advised salons and consumers to stop using these products until they have been reformulated and their safety documented. The maker of Brazilian Blowout products introduced Brazilian Blowout Zero, which the company says has been shown in independent tests to contain no formaldehyde.

The FDA is investigating the problem and urging salon professionals and consumers to report any adverse experiences to an FDA district office (phone numbers are available at or the agency's MedWatch adverse event reporting system (, or call 800-332-1088 to request a mail-in reporting form).

— Suzanne M. Olbricht, M.D.

Editorial Board Member

Harvard Women's Health Watch