Harvard Women's Health Watch

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.

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