No formaldehyde. No glyoxylic acid. How to check.

"Formaldehyde-free" is written on almost every bottle today. Here is what to ask to know that it is also true.

By the HER BOSS teamUpdated: September 2026Reading time: about 3 minutes

What formaldehyde is and why it was used

Formalin is a solution of formaldehyde, a substance that fixes proteins. In the early Brazilian straightenings it was what made the keratin seal in the hair. The problem: when heated by the flat iron, formaldehyde is released as a gas, and it irritates the eyes and airways and is classified as a carcinogen with prolonged exposure. The first to be harmed are hair stylists, who breathe it every day.

That is why the use of formaldehyde in cosmetics is restricted by regulation, and a straightening formula containing it above the permitted concentrations should not be sold in Israel.

The replacement that came instead, and its problem

A large share of "formaldehyde-free" formulas moved to glyoxylic acid. It fixes the keratin without releasing formaldehyde, and for years it was considered the clean solution. In recent years, medical reports have been published linking repeated straightening treatments with glyoxylic acid to kidney damage in some clients. The subject is still being studied, but it is a good enough reason to ask before the treatment not only "Is there formaldehyde?" but also "Is there glyoxylic acid?".

Three checks before you book

1. Registration with the Ministry of Health. Every cosmetic product marketed in Israel has a registration number. Ask for it. Herboss straightening is registered under number 0892026113912, in the hair and scalp products category.
2. The ingredient list. Look for formaldehyde, formalin, methylene glycol, glyoxylic acid. If one of them appears, it is not "free".
3. Who does the treatment. A good formula in unskilled hands gives a poor result. Ask whether the stylist has been trained on that specific formula.

How Herboss straightening seals without either

The Herboss straightening formula rests on two proteins, keratin and collagen, which seal inside the hair with controlled heat. The formula was developed over several years with some of the leading chemists in the country, is made in Israel under the supervision of the Ministry of Health, and is formaldehyde-free and glyoxylic-acid-free. The registration certificate is kept at every certified salon.

What the regulations in Israel say

Cosmetic products in Israel, straightening formulas included, must be registered with the Ministry of Health before they are marketed. The Ministry of Health limits the permitted concentration of formaldehyde in products, prohibits marketing straightening products that contain it above the permitted concentration, and from time to time publishes warnings about products found to contain excessive concentrations. A registration number is the client's way of knowing that the product has passed this check.

The picture is similar worldwide: the European Union restricts formaldehyde in cosmetics, and in the United States the FDA has issued warnings about straighteners that release formaldehyde and is working to restrict them.

How to read an ingredient list

The ingredient list (INCI) is written in English, from the largest ingredient to the smallest. Names that point to formaldehyde or to a substance that releases it when heated: Formaldehyde, Formalin, Methylene glycol, Methanal, Oxomethane, Oxymethylene, Paraformaldehyde. Glyoxylic acid and its derivatives: Glyoxylic acid, Glyoxyloyl carbocysteine, Glyoxyloyl keratin amino acids.

If one of them appears, it is not a "free" straightening. If the ingredient list is not available at all, that is a sign in itself.

What happens with exposure

Heated formaldehyde causes burning eyes, irritation of the throat and nose, coughing and difficulty breathing, and with repeated exposure it is classified as a carcinogen. The person most exposed is the hair stylist, every day, every treatment. As for glyoxylic acid, the medical reports of recent years dealt with temporary kidney damage in women who had repeated treatments. Both substances are outside the Herboss straightening formula.

For hair stylists: your station

• Work only with a formula that has a registration number and a visible ingredient list.
• Ventilation at the station, even when the formula is clean. Vapours from any product are still vapours.
• Gloves during application.
• Keep the registration certificate at the salon and show it to a client who asks. It sells.

Signs to watch for at the salon

• A sharp smell that stings the eyes during the straightening. Formaldehyde.
• A promise that "it is completely natural" with no registration number. There is no straightening without chemistry; there is safe straightening.
• Refusing to show the bottle or the ingredient list.

Frequently asked questions