During a keratin hair treatment, stylists apply a keratin-based product to the hair before using a flat iron to seal it in. This process can smooth frizzy or damaged hair, producing a sleek, shiny look.

Supporters of keratin hair treatments say they make hair more manageable and frizz-free. However, there are some potential side effects these products may cause, such as scalp and eye irritation.

In this article, we take a closer look at keratin hair treatments, including their benefits and cost. We also discuss safety concerns about their use.

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A keratin hair treatment is a process that helps straighten and smooth frizzy or damaged hair.

Keratin is a protein that the body produces naturally. It helps give structure and strength to the hair, skin, and nails.

Hair fibers consist of three main regions:

  • Medulla: This is located in the core of the hair fiber and can only be seen in larger or thicker hairs.
  • Cortex: This is the main component of hair. It contains proteins and provides mechanical support.
  • Cuticle: This thin protective outer layer consists of keratinized cells that overlap like scales.

Within the cortex, keratin forms a long helical chain with the help of chemical bonds, such as ionic bonding, disulfide bonding, and hydrogen bonding.

Also, weaker forces of attraction between molecules, which experts call van der Waals forces, can help maintain the a-helical keratin structure. Groups of these helical strands form filaments, which are the bulk of the cortex. The chemicals in keratin hair treatments target the keratin strands and alter their form.

During a keratin hair treatment, a stylist applies a keratin-based product to the hair and then uses a flat iron to seal it in.

Depending on hair thickness or length, as the chemicals diffuse into the hair, they alter the cross-linking of the keratin strands. The combination of chemicals, blow-drying, and flat ironing accelerates the cross-linking and turns curly or wavy hair straight.

After a keratin hair treatment, a person should avoid washing their hair for at least 2 days. They should also avoid:

  • putting their hair up in tight styles
  • using harsh shampoos and conditioners
  • exposing their hair to saltwater or chlorinated water

It is also important to use sulfate-free shampoo and conditioner to help prolong the treatment. These products are widely available in beauty supply stores, online, and in hair salons.

People should avoid washing their hair too often, as this can strip away the keratin treatment. Instead, aim to wash hair every 3–4 days using lukewarm, rather than hot, water. Applying a leave-in conditioner can also help protect the hair and keep it feeling moisturized.

When blow-drying, use a lower heat setting to avoid damaging the hair, and use a heat protectant product before using any hot styling tools.

It is also advisable to refrain from coloring the hair for at least 2 weeks after getting a keratin treatment. This allows the treatment time to set and helps prevent damage to the hair.

The effects of keratin hair treatments can last 12 weeks or longer. However, the results will eventually fade, and an individual will need to repeat the treatment to maintain straight, smooth hair.

At-home or professional keratin hair treatments have several benefits:

Hair appears shinier

Keratin hair treatments smooth the hair cuticle, making it less frizzy. In addition, many people find that the treatment gives the hair a naturally smooth, shiny look.

Results can last a while

If a person cares for their hair appropriately, uses suitable products, and does not wash it too frequently, results of the treatment can last up to a few months.

Hair becomes more manageable

People with particularly frizzy or thick hair may choose a keratin hair treatment because it can help them cut down on styling time and make their hair more manageable.

Individuals may also find that after the treatment, their hair dries more quickly. This in turn can reduce heat exposure, which can improve hair health.

Hair does not break as much

Keratin is a structural protein, and therefore, it can strengthen hair and reduce breakage. Some people say that treatments help their hair grow faster, as the ends are not splitting or breaking.

Keratin hair treatments are rather expensive. A person can expect to pay up to $400 or more, depending on their hair and the salon. They may also need to buy potentially costly specialized hair products.

Additionally, the treatment might require a time commitment of several hours at the hair salon.

Also, if an individual prefers to wash their hair every day, the treatment may not be right for them.

A considerable advantage of keratin hair treatments is their long lasting effects. They can greatly reduce the time spent styling the hair every day, particularly if the hair is frizzy or thick. The effect can last 12 weeks or more.

Moreover, some individuals no longer need to heat style their hair. This is because after the treatment, hair dries naturally straight and appears glossy and smooth.

There has been some controversy surrounding keratin treatments, because they use formaldehyde or other chemicals that release formaldehyde. Formaldehyde is a colorless, pungent gas that has toxic properties.

Formaldehyde may have harmful health effects if a person inhales it or if it comes into contact with the eyes or skin.

The harmful effects may include:

Experts also associate repeated exposure to high levels of formaldehyde with some types of cancer, including leukemia. However, further research is necessary to determine the link between leukemia and formaldehyde exposure.

Some products state they are formaldehyde-free. However, they use methylene glycol or other chemicals instead, which may release formaldehyde when heated. This means that even though formaldehyde is not on the list of ingredients, people may still be at risk of exposure to the chemical.

The Cosmetic Ingredient Review Expert Panel has set the maximum safe concentration of formaldehyde to be less than 0.2%.

Yet, some Brazilian keratin treatments may contain much higher levels — in some cases, more than five times higher — than the recommended level.

The Environmental Working Group lists Brazilian-style keratin treatments with formaldehyde and those using formaldehyde alternatives as not safe.

Additionally, keratin hair treatments can damage hair. That is why people should use them sparingly and avoid repeated exposure to harsh chemicals and heating elements.

It is also of note that pregnant people should not use keratin hair treatments.

Keratin hair treatments smooth the hair, making it look shiny and appear frizz-free. People report that it can make hair more manageable. Although these treatments are costly, results can last up to a few months.

However, despite their popularity, keratin hair treatments are not without risks. Most contain formaldehyde or other ingredients that may release formaldehyde. These chemicals can cause side effects, such as allergic reactions, coughing, and vomiting.