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- and long-term effects that may impact your health.

What Happens During the Hair Smoothing Process? 

Your stylist usually applies a hair straightening or smoothing solution to your hair and 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, and 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 and is present in the air at levels exceeding 0.1 ppm, it can cause serious irritation of your eyes, nose, and lungs. It can also cause skin sensitivity or allergic dermatitis.

Formaldehyde Exposure: Potential Short-and Long-Term Effects

The greater the exposure to products that contain formaldehyde in terms of both length of time and 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 and dizziness), respiratory tract problems (sore or scratchy throat, cough, wheezing), nausea, chest pain, vomiting, and 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) and 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 and 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, and do you know the necessary safeguards to minimize exposure to formaldehyde? May I see your training certificate from the manufacturer and the directions for product use? Does the salon have proper ventilation? Do you periodically test the air for adherence to the Occupational Safety and 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 and 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 and adverse reporting program. You also may call MedWatch at 1-800-332-1088 to request a reporting form by mail.

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

​Find out which smoothing treatment is the best.

A smoothing treatment can be a worthwhile investment for anyone with frizz-prone hair. So while salon services like a Brazilian blowout or a keratin treatment can set you back $250 on average, they'll give you smooth, shiny hair that'll last for months.

Both treatments will spare you the time you've been wasting styling your hair with frizz-fighting products that never quite seem to work. So, what's the difference between the two, and which one should you get? InStyle turned to Christina B. of New York City's Rita Hazan Salon to spell it out.

What's the Difference Between Brazilian Blowouts and Keratin Treatments?

Brazilian blowouts and keratin treatments essentially have the same effect on hair: both eliminate frizz and boost shine. They're safe for all hair types and can be done on color-treated hair. However, Brazilian blowouts are more customizable.

"Since the market is so saturated with keratin treatments you could spend hours googling what you think would be best for the look you're after, but the Brazilian blowout can be adjusted for different hair textures," explains Christina B. "The stylist can flat iron the hair at different temperatures and achieve different looks."

What this means is that if you don't want your hair completely straight, your stylist can tailor the treatment so that your natural hair texture isn't completely lost. They'll still seal the treatment with a 450 degree flat iron, and you'll still have smooth, voluminous waves when they're all done.

The other way the treatments vary is in their downtime. Following a keratin treatment, it's recommended that you don't tie your hair up and you can't wash it for three or four days. As for a Brazilian blowout, you can go about your regular styling routine.
 
What Should I Know About What's In These Smoothing Treatments?

Although a Brazilian blowout has its benefits, the treatment can't be mentioned without addressing the controversy surrounding it. There has been concern about the formaldehyde in its formula.

"I find that if they're done properly and in well ventilated areas they are not harmful at all," says Christina B. "But you can find formaldehyde-free versions if you are worried about that."
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Whichever treatment you do choose, research salons in your area that offer the service to find one that's reputable. You'll get the results you want without sacrificing the health of your hair.