A keratin treatment can tame frizz and cut your styling time for months. Here is how it works, how to make it last and the safety questions to ask before you book.
What is a keratin treatment?
A keratin treatment is a salon smoothing service. Your stylist applies a smoothing solution to your hair and then seals it in with heat, usually with a flat iron. A dermatologist interviewed by the Cleveland Clinic describes it as a chemical process that smooths the outer layer of the hair shaft. People book it to cut frizz, add shine and make blow-drying faster.
You may also hear the term Brazilian blowout. That is a brand name, but many people use it to mean any smoothing treatment. Formulas vary a lot, so the name on the menu tells you less than the actual product the salon uses.
Keratin smoothing is not the same as a relaxer or Japanese straightening. Those services are meant to change the hair for good, so treated hair stays straight until it grows out. A smoothing treatment fades over time. And if you only want smooth hair for a few days, a blowout uses no chemicals at all.
How long does a keratin treatment last?
It depends on the product, your hair and how often you wash it. Results fade gradually rather than all at once. The Cleveland Clinic says results can last about six months if you don't wash your hair too often. Washing more often can shorten that, so ask your stylist what to expect for your hair.
Plan for a long appointment. The service includes washing, applying the product, letting it sit, drying and flat ironing in small sections. The Cleveland Clinic describes the process as lengthy, with timing that depends on how much hair you have and its texture. Ask how long to set aside when you book.
How do you care for your hair after a keratin treatment?
Aftercare varies by product, so follow your stylist's instructions first. These general tips help:
- Wait before your first wash. The Cleveland Clinic suggests waiting a few days before the first shampoo. Your stylist will tell you exactly how long for your product.
- Wash less often. Fewer washes help the results last.
- Use gentle products. The Cleveland Clinic suggests products free of sodium chloride, which is salt. Ask your stylist which shampoo and conditioner to use.
- Ask about ponytails, clips and tucking hair behind your ears. Some products need hair left loose and straight for the first few days.
- Keep heat moderate when you style. Your hair may dry smoother and faster than before, so you may not need as much heat.
Is formaldehyde in keratin treatments a concern?
It can be, which is why it's worth asking questions. The FDA says hair smoothing products often contain formaldehyde, which may be listed as formalin or methylene glycol. When the product is heated with a blow dryer or flat iron, formaldehyde is released into the air as a gas.
The FDA lists health effects that have been reported, including eye irritation, headaches, dizziness, sore throat, cough, wheezing, nausea, chest pain, vomiting and rash. It also notes that formaldehyde is classified as a human carcinogen by the International Agency for Research on Cancer, based on links to certain cancers at high or long-term exposure.
Labels don't always tell the whole story. In a hazard alert for salons, OSHA reported finding formaldehyde in the air above its safety limits in salons using smoothing products, including some labeled formaldehyde-free. OSHA also lists other names formaldehyde can go by, such as methylene glycol, formalin and methanal. OSHA's alert is aimed at salon workers, who may do these services again and again.
Has the FDA banned formaldehyde in hair straightening products?
Not as of October 2026. In 2023, the FDA put a planned rule on the federal regulatory agenda that would ban formaldehyde and formaldehyde-releasing chemicals, such as methylene glycol, in hair smoothing and straightening products that are heated on the hair. The target date for publishing the proposal has been pushed back several times.
The most recent federal regulatory agenda entry lists November 2026 as the target for the proposed rule. As of late October 2026, it had not been published in the Federal Register, and no nationwide ban was in effect. Even after a proposal is published, the public gets a chance to comment before the FDA decides on a final rule.
Some states set their own rules. In Washington State, for example, the law has restricted formaldehyde in cosmetics since January 1, 2025, and limits on formaldehyde-releasing chemicals take effect January 1, 2027, according to the Washington Department of Ecology.
What should you ask the salon before a keratin treatment?
A good salon will be glad you asked. The FDA suggests asking about the product, its safety data sheet, the stylist's training and the salon's ventilation. Bring these questions to your consultation:
- What is the name of the product, and does it contain formaldehyde, formalin or methylene glycol?
- Can I see the product's safety data sheet (SDS)? OSHA requires salons to keep SDSs available to their workers, so the salon should have one on hand.
- How is the room ventilated during the service?
- Have you been trained on this product?
- Do you offer a product that doesn't release formaldehyde when heated?
- How long should I wait to wash, and which products should I use after?
- Will this loosen my curls, or mostly reduce frizz?
Who should check with a doctor first?
If the stylist isn't sure whether a product contains formaldehyde, the FDA says you may not want to use it, especially if you've had a reaction before.
The Cleveland Clinic says keratin treatments aren't recommended during pregnancy, and that people with sensitive skin or allergic contact dermatitis should be cautious. If you are pregnant, have asthma or other breathing problems, or have reacted to hair products before, talk with your doctor or a dermatologist before you book.
If you notice symptoms during or after a treatment, such as burning eyes, coughing or a rash, tell your health care provider. You can also report a reaction to a cosmetic to the FDA.
Ready to compare options? Browse keratin smoothing salons near you and bring your questions to a consultation.
Questions people ask
Is a keratin treatment the same as a Brazilian blowout?
Brazilian Blowout is a brand name for one smoothing treatment, but many people use the term for any keratin-style smoothing service. What matters most is the exact product the salon uses, so ask for its name and ingredients.
Are formaldehyde-free keratin treatments really formaldehyde-free?
Not always. OSHA has found products labeled formaldehyde-free that still released formaldehyde during use. Ask for the product name and its safety data sheet, and look for other names such as methylene glycol and formalin.
Will a keratin treatment straighten curly hair?
It depends on the product and method. Some treatments mainly reduce frizz, while others loosen curls more. Results fade over time. Tell your stylist if you want to keep your curl pattern.
Can I color my hair and get a keratin treatment?
Usually, but timing matters. Many stylists prefer to color first and then smooth. Ask your stylist how to schedule the two services for your hair.
Is the FDA banning keratin treatments?
Not keratin treatments as a whole. The FDA has planned a rule to ban formaldehyde and formaldehyde-releasing chemicals in heated hair smoothing and straightening products. As of late October 2026, the proposed rule had not been published, and its listed target date was November 2026.
