Woman with straight hair
April 11th 2025

Keratin straightening with formalin: Consequences for the hair

Resorting to permanent straightening treatments has become a very common practice. However, one of the ones that has generated the most expectation and debate is the one known as keratin straightening with formalin. Is it true that this hair straightening treatment is harmful? What are the effects of keratin straightening with formalin on the hair?

At blog de Hospital Capilar, hair clinic in Spain experts in hair grafting in Madrid, Murcia and Pontevedra, we tell you to what extent keratin straightening with formalin is harmful to the scalp and hair.  

What does keratin smoothing with formalin consist of?

Keratin is a protein found naturally in our body. It is the main component of hair and nails. Current keratin treatments are used topically with the aim of repairing the hair fiber and nourishing the hair. However, on many occasions this type of hair treatment is also used to straighten the hair, since it enhances the straightening.

Among the types of straightening is the one that contains formalin. Formalin is a very volatile and toxic chemical compound that we can find in some hair products. When it is found in amounts below 2%, it does not pose any health risk, but above this percentage it can cause serious problems.

The use of keratin straightening with formalin was extended due to the effectiveness in the results, since when applied to the hair it achieves a perfect straightening and reduces frizz. Keratin straightening without this chemical compound is also effective, for this reason we recommend resorting to these since we will be considerably reducing possible risks to hair health.  

Is keratin straightening with formalin harmful?

As we have mentioned, keratin straightening with formalin can be the cause of problems in the scalp, among others. Although it is true that using it correctly and in the hands of a professional is safer, we recommend opting for other types of hair straightening treatments with less impact on our hair health.

The problems that keratin straightening with formalin can cause in the hair are several. Below we tell you the most common.

Allergic reactions

Although it can occur with any other type of product, keratin straightening with formalin can cause notable allergic reactions, not only at the skin level, but also when breathing this substance, which, as we have mentioned, is highly volatile.

Scalp sensitivity and irritation

If formalin is applied to the scalp and not just from the middle to the ends, it can cause irritation and sensitivity.

hair thinning  

One of the most frequently asked questions regarding this method is whether formalin keratin straightening causes hair loss. It is not related to any type of alopecia, but it can weaken the hair fiber, causing the hair to break easily. However, a bad practice could also cause the hair follicles to weaken, causing the hair shaft to detach, although it is not usually the usual type of fall associated with this treatment.

In people with hair that is already weakened, fine or with hair loss problems, it is not recommended to abuse keratin straightening with formaldehyde as it can aggravate the hair problem in question. 

What is hair density

Other less damaging hair straightening methods

There are other options to achieve the straightening we want without having to resort to such strong chemical compounds.

Keratin straightening without formaldehyde

Formaldehyde-free keratin straightening is another of the most demanded methods, especially to nourish, repair and obtain quality hair in terms of its structure and silkiness. It is recommended that it be a professional who performs them in a beauty salon or hairdresser.

Use of thermal protectors

A less expensive option is to use the iron and the dryer. If we use heat sources on a regular basis, it is important to apply a thermal protector first to reduce the impact on the hair.

What to do in case of unusual hair loss?

Keratin straightening with formalin is not considered a common cause of alopecia, but there are other types of factors that are more common in terms of the development of hair loss. Knowing what causes hair loss is essential to find a solution, especially in cases of irreversible hair loss to avoid a greater visual impact.

Medical diagnostic

It is recommended that, in the event of hair loss that is accompanied by a lack of density or areas without hair, we go to a hair clinic in Spain. In this way, medical professionals will be able to determine the cause and apply the most appropriate treatment accordingly.

Hair treatments to stop hair loss

Currently there are medical hair treatments aimed at curbing hair loss. In Hospital Capilar we have the Hair Redensification Treatment and the Capillary Regeneration Treatment with which to treat the problem of hair loss and obtain quality, healthy and deeply cared for hair.

Hair transplant, the method to recover hair

In cases where this hair loss already accompanies hairless areas and baldness, the only way to recover the hair is with the FUE hair graft. It is an outpatient technique, minimally invasive, through which the necessary follicles are extracted from the donor area to implant them in the area affected by baldness.

The results of the capillary implant are given definitively one year after the intervention, although the first changes can be seen already at 6 months.

Hair mesotherapy in Spain

En Hospital Capilar we take care of your hair in depth

Do you suffer from unusual hair loss? Do you notice a lack of density? In Hospital Capilar We have an expert medical team that will respond to your needs and you will obtain the results you expect. Request your medical diagnosis at no cost!

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