What is keratin and how does it affect hair?

Keratin and its associated protein (KAPs), are regarded as the main structural components of hair. There are two types of keratin protein naturally present in our body that are commonly referred to as the soft epithelial keratins and the hard epithelial keratin. Hard keratin is mostly found in tissues such as skin, cornea, hair, and nails. On an estimate, 80% of human hair is formed by an α‐keratin protein that is responsible for the properties such as hair strength, flexibility, durability, and functionality. With excessive hair bleaching, ironing, and other draining procedures that affect the hair strand, this protein denatures and gives a dry, rough, fragile, and dull, appearance to the hair.  

This may be the reason why we observe a wide variety of products ranging from shampoos to conditioners and serums and supplements that endorse keratin as their key element, as well as specialized keratin treatments.

Keratin treatment

Artificial preparations of keratin are usually driven from the feathers, horns, and wool of different animals. Keratin treatment consists of mixing this protein preparation with a chemical called formaldehyde and applying it to the hair. It is then sealed in with the help of flat ironing.  This semi-permanent treatment smoothens the cuticle due to the added protein and gives hair a temporary straight smooth and lustrous appearance. 

Many commercial brands and salons promote keratin treatment to be a procedure with no damaging consequences on your hair and scalp. However, experts say that this might not always be true.

Benefits of keratin treatment

Keratin treatment is known to provide a temporary luster, and smoothness to the hair which typically fades out after a few months. Unlike the straightening/rebonding process, the volume of the hair is not extensively reduced, although people with extremely curly hair or wavy hair may experience a slight loss in curls and have straighter hair afterwards. However, these results vary from person to person.

Keratin products are advertised as able to fill the porous hair strand with protein, thus restoring its strength, structure, and shine. 

Possible risks and side effects of keratin treatment

Although keratin is a naturally occurring protein in our body, when artificially added it may impart some side effects. These artificial keratin preparations are derived from animal sources with the further addition of certain chemicals that may not be healthy for all hair. One of the most common components is a chemical known as formaldehyde that is either present on its own, or released by the reaction of other elements present in such products. According to the American Cancer Society, Formaldehyde is a well-recognized carcinogen, with a high risk of blood cancers such as leukemia and other cancers of the nasal cavity. Individuals most exposed to formaldehyde are the hairstylist working with keratin treatment products. Nosebleeds and respiratory complaints have been reported as a consequence of formaldehyde inhalation and contact over time. This is one of the reasons why pregnant females, individuals with formaldehyde sensitivity, and prior respiratory complaints are advised not to opt for keratin treatments.  

A study published in 2012, reviewed seven renowned keratin treatment products commercially marketed, and found that six out of these seven products contained a high concentration of formaldehyde that was between 0.96%-1.4%. These values are five times higher than the recommended national safety standards of 0.2 percent.  

In addition, the high heat employed during keratin treatments to secure the protein, also has the potential to damage hair, by breaking down the natural keratin structure in hair strands. This may lead to a loss of natural hair keratin and eventually premature har shedding. Keratin treatments are not the only cosmetic products that contain formaldehyde. It can also be found in products such as nail polish, nail polish removers, hair dyes, hair glues, shampoos, etc. 

However, it’s important to note that long-term side effects and consequences of keratin treatment still need to be studied and analyzed in further detail.

Other keratin containing products

Keratin serums, shampoos, and conditioners

The results observed from using Keratin serums, shampoos, and conditioners are significantly milder than salon treatments, however, most of these products are comparatively safer and less damaging to hair than certain treatments. 

Keratin supplements

Over-the-counter keratin supplements are also widely available, and may be found in both powder and capsule form. However, as this protein is highly resistant to digestive enzymes, the efficacy of oral supplements remains controversial. On the other hand, several dietary products that are rich in keratin can be made a part of a regular diet to enhance its absorption from the gut. These include egg, salmon, sweet potato, sunflower seeds, kale, and mangos, etc.


Whether keratin treatments are more beneficial than harmful is still a topic of debate, as both the data of its efficacy and side effect profile remain lacking. However, some of the keratin interventions that are safe to be added to your hair care routine include consumption of a balanced diet rich in essential vitamins, minerals, and marine protein, cleansing and conditioning hair regularly with gentle densifying shampoo that contains Biotin, Zinc, and Keratin to achieve a smooth, shiny and thick looking hair.



Maneli MH, Smith P, Khumalo NP. Elevated formaldehyde concentration in “Brazilian keratin type” hair-straightening products: A cross-sectional study. Journal of the American Academy of Dermatology. 2014 Feb 1;70(2):276-80.

Tinoco A, Gonçalves J, Silva C, Loureiro A, Gomes AC, Cavaco‐Paulo A, Ribeiro A. Keratin‐based particles for protection and restoration of hair properties. International journal of cosmetic science. 2018 Aug;40(4):408-19.

Swenberg JA, Moeller BC, Lu K, Rager JE, Fry RC, Starr TB. Formaldehyde carcinogenicity research: 30 years and counting for mode of action, epidemiology, and cancer risk assessment. Toxicologic pathology. 2013 Feb;41(2):181-9.

Langbein L, Schweizer J. Keratins of the human hair follicle. International review of cytology. 2005 Jan 1;243:1-78.