two photos of women of different hair-types, both having their hair straightened with flat irons

If you decide that you want to make your hair less frizzy or straighter, you may choose to go to a professional stylist at a hair salon for a hair straightening or smoothing service. Most hair smoothing or straightening products release formaldehyde gas, a known human carcinogen as classified by the International Agency for Research on Cancer, into the air during the hair straightening or smoothing process. Formaldehyde exposure can cause both short- & long-term effects that may impact your health.

This page provides information about: 

  • What Happens During the Hair Smoothing Process
  • Why Exposure to Formaldehyde is Dangerous
  • Formaldehyde Exposure: Potential Short- & Long-Term Effects
  • Steps to Take If You’re Thinking of Using Hair Smoothing Products

What Happens During the Hair Smoothing Process? 

Your stylist usually applies a hair straightening or smoothing solution to your hair & follows it with a heat processing step—typically performed with a flat iron device that seals the solution into the strands of the hair. When the solution is heated, the formaldehyde in the product is released into the air as a gas. If the salon is not properly ventilated, you, your stylist, & others in the salon are at risk of inhaling the released formaldehyde.

Why Exposure to Formaldehyde is Dangerous

When formaldehyde is released into the air & is present in the air at levels exceeding 0.1 ppm, it can cause serious irritation of your eyes, nose, & lungs. It can also cause skin sensitivity or allergic dermatitis.

Formaldehyde Exposure: Potential Short-& Long-Term Effects

The greater the exposure to products that contain formaldehyde in terms of both length of time & concentration, the higher the potential health risks. Individuals who have experienced formaldehyde exposure have described reactions such as eye problems or irritation, nervous system problems (for example, headaches & dizziness), respiratory tract problems (sore or scratchy throat, cough, wheezing), nausea, chest pain, vomiting, & rashes. Chronic effects associated with formaldehyde can include an increased prevalence of headaches, asthma, contact dermatitis (a red, itchy rash caused by direct contact with a substance or an allergic reaction to it as a result of sensitization) & possibly cancer.

It’s important to note that some people are very sensitive to formaldehyde, whereas others have no reaction to the same level of exposure. If you are sensitive to formaldehyde, you should not use this type of product.

Steps to Take If You’re Thinking of Using Hair Smoothing Products 

  1. Don’t do it yourself. Don’t apply them yourself at home. Go to a licensed hair professional in a salon. Hair professionals should be trained to take precautions such as wearing gloves & safety glasses, as well as making sure that there is proper ventilation when applying hair smoothing products. For more information, please visit OSHA Hair Salons: Facts about Formaldehyde in Hair Products.
  2. Read the list of ingredients. While the FDA discourages consumers from buying these products for home use, if you are considering purchasing a product from a store or online to apply yourself, read the required list of ingredients. If there isn’t one, don’t buy the product. If the hair smoothing product lists one of these ingredient names on the packaging or company website: formaldehyde, formalin, or methylene glycol, then it means the product contains formaldehyde or will release formaldehyde. Of note, not all hair smoothing products contain formaldehyde, which is why you need to read the label to see what is in the product. 
  3. You may also want to ask your salon professional these questions: Does the product contain formaldehyde? Is there an ingredient list available for this product that I could read? Would it be possible for me to review the Safety Data Sheet for this product?  Have you been trained to apply this product, & do you know the necessary safeguards to minimize exposure to formaldehyde? May I see your training certificate from the manufacturer & the directions for product use? Does the salon have proper ventilation? Do you periodically test the air for adherence to the Occupational Safety & Health Administration’s limits for formaldehyde? Do you have an alternative hair smoothing product that does not release formaldehyde when heated?
  4. Report bad reactions. If you experience a bad reaction to a hair smoothing product, stop using the product & report your symptoms to your health care provider. You can also report your symptom to the FDA by contacting the Consumer Complaint Coordinator in your area or by  reporting them online at MedWatch, the FDA’s safety information & adverse reporting program. You also may call MedWatch at 1-800-332-1088 to request a reporting form by mail.

See a fact sheet & an infographic for more information about hair smoothing products & formaldehyde.