Is Keratin Safe? Formaldehyde, Side Effects and Who Should Wait
Keratin treatments can be done reasonably safely, but only when the product, the ventilation and your own health line up. The main concern is formaldehyde: some smoothing formulas contain it or release it as a gas when heated, and that is what causes most of the reported problems. Below we explain what the evidence says, who should hold off, what to do about coloured or bleached hair, and the exact questions to ask any Dubai salon before you sit down.
TL;DR
- Keratin smoothing is not risk-free. Some formulas contain formaldehyde or ingredients that release it when heated, which can irritate the eyes, nose, throat and skin.
- “Formaldehyde-free” on a label does not guarantee no exposure, because some products use releasers such as methylene glycol.
- Skip it during pregnancy, and be careful if you have sensitive skin or contact dermatitis.
- On coloured or bleached hair, the question is less about danger and more about hair condition and timing. Space the services out.
- Ask for the product’s safety data sheet, check the room is ventilated, and book a consultation first.
Table of Contents
- What a keratin treatment actually does
- Why formaldehyde is the main concern
- Keratin treatment side effects
- Keratin during pregnancy
- Keratin on coloured, dyed or bleached hair
- What happens to hair over the following months
- How to make a keratin treatment safer
- Our view at the salon
- Keratin smoothing at Boost Beauty Lounge
- FAQ
- Sources
What a keratin treatment actually does
A keratin (or protein, or “botox”) smoothing treatment coats the hair with a formula, then seals it in with a flat iron. The result is smoother, less frizzy hair that can hold for a few months. The name is slightly misleading: the active smoothing work is usually done by a chemical agent, not by the keratin protein itself. Cleveland Clinic notes that results can last about six months if you do not wash your hair too often, and that treatments may affect your natural curl pattern.
That chemical agent is where the safety question starts. The heat step matters too, because it is when some ingredients turn into airborne gas.
Why formaldehyde is the main concern
The US Food and Drug Administration explains that hair smoothing products often contain formaldehyde, also listed as formalin or methylene glycol, and that when heated it is released into the air as a gas. The same page says air levels above 0.1 ppm can irritate the eyes, nose and throat, and that high or prolonged exposure has been linked to certain cancers.
Two points follow from this:
- The person with the most exposure is usually the stylist, who breathes the fumes through repeated services. You, as a client, have shorter exposure, but a poorly ventilated room raises it for everyone.
- The risk depends on concentration and conditions, not just on the word “keratin”. A well-made, low-release product in a ventilated space is a very different situation from an unlabelled product heated in a small closed room.
In the United States, the Cosmetic Ingredient Review panel concluded that using formaldehyde or methylene glycol in hair straightening products is unsafe at the concentrations present and the way they are used. That is a strong statement, and it is the reason a careful client should ask questions rather than assume.
“Formaldehyde-free” is not always what it sounds like
This is the part that surprises most people. The same California document notes that products labelled formaldehyde-free may still contain formaldehyde or releasers such as methylene glycol. A published case report went further, linking a formaldehyde-free straightening product to chemicals that can release formaldehyde when heated and may produce oxalate, which can injure the kidneys (acute kidney injury case report).
A case report is one patient, not proof of how common the problem is. In the UAE, doctors speaking to Khaleej Times said hair straightening may cause minor skin irritation and, rarely, kidney problems, and that no serious related cases had been observed in the country. Both statements can be true: serious harm looks uncommon, and it is still worth choosing carefully.
If you want to understand how releasers hide on ingredient lists, this guide to spotting formaldehyde releasers is a practical starting point. We also compare the two most common labels in our article on Brazilian blowout versus keratin and checking formaldehyde before heat.
Keratin treatment side effects
Most reactions are short-lived and relate to irritation. The FDA lists possible effects including eye irritation, headaches, respiratory problems, nausea, rash and allergic dermatitis. Cleveland Clinic adds that keratin hair treatments can sometimes cause hair damage and loss, chest pain, coughing, eye irritation, nausea and vomiting, rashes and respiratory problems.
A 2021 academic review gives a useful sense of proportion. It reports that irritant and allergic contact dermatitis are the most common adverse events, while scarring alopecia is rare. It also warns that excessive or improper use may cause telogen effluvium (temporary shedding), and that long exposure, incorrect pH or high concentrations can cause hair breakage.
In plain terms:
| Reaction | How common | What it looks like |
|---|---|---|
| Eye, nose and throat irritation | The most typical complaint | Watering eyes, burning, coughing during or just after the service |
| Scalp or skin irritation, allergic dermatitis | The most common adverse events in the review | Redness, itching, rash around the scalp, neck or ears |
| Hair breakage or shedding | Linked to wrong pH, long exposure or high concentration | Snapping hair, thinning in the weeks after |
| Headache, nausea | Reported in FDA list | Often tied to fumes in a poorly ventilated room |
| Kidney injury, scarring alopecia | Rare, described in case reports and reviews | Needs medical attention |
If you get breathing difficulty, severe swelling, chest pain or a spreading rash, leave the room, get fresh air and see a doctor or go to an emergency department. Do not wait for it to pass.
Keratin during pregnancy
This one is simple. Cleveland Clinic states that keratin treatments are not recommended during pregnancy. Since the main concern is inhaled fumes, the sensible approach is to postpone the service until after pregnancy and, if you are breastfeeding, to ask your doctor or midwife for advice on timing. If you are expecting and wondering about colour instead, we have covered that separately in our guide to hair colouring in pregnancy.
The same Cleveland Clinic page says people with sensitive skin or allergic contact dermatitis should proceed with caution. If you have eczema on the scalp, a history of reacting to hair dye, or asthma that flares with strong smells, speak to your GP or dermatologist first and tell your stylist before any product is opened.
Keratin on coloured, dyed or bleached hair
People search this a lot, and it is the question we hear most at the salon. Colouring and smoothing both change the hair fibre. A 2024 review of chemical treatments says colouring can affect hair integrity, often increasing porosity and dryness and changing the structure of the hair, which is why it calls for cautious application and proper aftercare.
So keratin on dyed hair is possible, but the order and the gap matter:
- Colour first, then smooth, with a gap. We suggest waiting around 10 to 14 days between the two. Our article on keratin on coloured hair and salon safety explains the reasoning.
- Give bleached hair longer and a strand test. Heavily lightened hair is porous and can break under heat. Ask your stylist to test a small section and judge elasticity before committing.
- Do not stack services on the same day if your hair already feels dry, stretchy or rough when wet.
There is some reassuring research on recovery. In one case study of permanent dye, the hair cuticle showed near-complete restoration after eight weeks. It is a single case, not a promise, but it supports the idea that a pause between services helps.
If you are new to a dye, do a patch test first. We explain how in our 48-hour hair dye allergy test guide for Dubai. And if hair already snaps after colour, read how to protect it in the first 72 hours before booking anything else.
What happens to hair over the following months
Smoothing gradually fades as you wash. Expect the most sleek result in the first weeks and a slow return of natural texture, possibly up to around six months if you wash gently. The aftercare matters for both safety and results. Follow your stylist’s advice on when to wash for the first time; our guide to washing hair after keratin suggests following your stylist and waiting 48 to 72 hours. For keeping the finish, see how to keep smoothed hair sleek.
In Dubai, two local factors can undo a smoothing service faster than you expect: constant air conditioning and hard water. Both dry out hair, and dry hair is more fragile under heat. We cover them in salon treatment for air-conditioning-dry hair and hair treatment for hard water damage.
How to make a keratin treatment safer
You cannot remove risk entirely, but you can lower it a lot. Before you book, work through this list.
Questions to ask the salon
- Does the product contain formaldehyde, formalin, methylene glycol or any releaser? The FDA says consumers can ask salon professionals whether a product contains formaldehyde-related ingredients, and that hazardous products have a Safety Data Sheet. Ask to see it.
- Is the product registered and sold by a known supplier? An unlabelled tub decanted into a jar is a red flag. A Health Ministry warning in Israel about unregistered straighteners found formaldehyde, a carcinogen prohibited in cosmetics, in the products. It is a different country, but the lesson about unregistered products travels.
- Is the area ventilated? The FDA says that if salons are not properly ventilated, clients and professionals risk inhaling released formaldehyde. Open doors, extraction fans and a service area away from the waiting seats are all good signs.
- Will you test a strand and assess my hair first? A good stylist looks at porosity, previous colour and breakage before choosing a formula and a heat setting.
- What is the aftercare plan? Washing timing, shampoo choice and what to avoid should be explained clearly, in writing if possible.
During and after the service
- Tell the stylist immediately if your eyes sting, your throat burns or you feel dizzy.
- Step outside for fresh air if needed. A short pause is better than pushing through.
- Avoid tying hair tightly or using hot tools hard in the first days, as your stylist advises.
- If your scalp reacts or hair starts shedding heavily, see a dermatologist instead of trying another product.
What about at-home kits?
Cleveland Clinic says at-home keratin kits are available, but that you should read all instructions beforehand and follow them closely. Our view is that the heat step is where home use gets risky, since most bathrooms are small and poorly ventilated. If you do use a kit, open a window, run an extractor fan and never skip a patch test.
Our view at the salon
We do not think the honest answer to “is keratin safe” is a flat yes or no. It is “safe enough for most healthy adults when the product is known, the room is ventilated and the hair is ready”, and not at all for someone who is pregnant or reacts to chemicals. That is why we plan every service around a consultation before anything else, with the stylist looking at your hair history, your scalp and what you want to achieve.
We also think a client should never feel awkward asking what is in the bottle. If a salon dodges that question, treat the answer as a no. Our packages are fixed-price, you pay after the service is completed, and we give home-care guidance plus a 10-day satisfaction guarantee. The point of all this is the same: you should be able to decide calmly, not under pressure in the chair.
If your hair is freshly bleached, damaged or very dry, we would rather tell you to wait and treat it first than sell you a smoothing service that day. A good result in three weeks beats a risky one today.
— Boost
Keratin smoothing at Boost Beauty Lounge
Our Keratin/Protein/Botox Package costs AED 1,299 as a fixed price for any hair length, and it starts with a consultation so we can plan around your colour history and scalp. You pay after the service. You can find us in Deira, one minute from Salah Al Din Metro Exit 1, and book by WhatsApp or phone through the salon page. If you also want colour, our Hair Package lets you plan the two services with the right gap between them.
FAQ
Is a keratin treatment harmful to your hair?
It can be, when the formula is too strong, left on too long or applied to hair that is already weak. The 2021 review says long exposure, incorrect pH or high concentration may cause breakage, and excessive use may cause shedding. Applied correctly to healthy hair, most people see smoother hair rather than damage.
Who should not have a keratin treatment?
Anyone who is pregnant should postpone it, and people with sensitive skin, allergic contact dermatitis or breathing conditions should speak to a doctor first. Avoid it too if your scalp is irritated or broken, or if your hair is currently snapping from bleaching or colour. Tell your stylist about any previous reaction.
Can you do keratin on dyed or bleached hair?
Yes, in most cases, but not on the same day and not on hair that is already fragile. We suggest leaving 10 to 14 days after colouring and doing a strand test on bleached hair. Your stylist should decide based on how your hair behaves, not on a fixed rule.
Is a formaldehyde-free keratin treatment completely safe?
No. Some products labelled formaldehyde-free contain releasers such as methylene glycol, which can still give off formaldehyde when heated. Ask for the ingredient list and safety data sheet rather than relying on the front label.
Sources
- What You Need to Know About Keratin Treatments, Cleveland Clinic
- Keratin: Protein, Structure, Benefits, Uses & Risks, Cleveland Clinic
- Hair Smoothing Products That Release Formaldehyde When Heated, FDA
- Decision Document for Hair Straightening Products, California DTSC
- Acute Kidney Injury following Exposure to Formaldehyde-Free Hair Straightener
- Straight to the Point: What Do We Know So Far on Hair Straightening
- UAE doctors on hair straightening and kidney issues, Khaleej Times
- Effects of Chemical Treatments on the Hair Shaft and Scalp
- Ultrastructural study of hair fibre damage and restoration after dyeing, PubMed
- Health Ministry warns against hair products, Ynetnews
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