What Is Keratin?

This naturally occurring protein protects your hair, skin, and nails

Keratin is a protein in the cells on the surface of the skin. The fingernails, hair, and skin need keratin to grow, function, and stay healthy. The protein helps protect these structures from damage and may also be part of the healing process.

The body naturally makes keratin. It's also found in the hooves, wool, and feathers of animals. It can be extracted from these sources and used for supplements, treatments, and other products to help with hair, skin, and nail health.

Hair and many hair products contain keratin
 jun xu / Getty Images

Types of Keratin

There are 54 types of keratin genetically encoded by the human genome and produced by the body. Out of the 54 types, half of them reside within hair follicles all over the body.

Type I

Type I keratins are categorized as being the smaller and more acidic type of keratin.  They are separated into two groups that work together functionally towards the common goal of epithelial cell health.

Type II

Type II keratins are larger than their type I counterparts and have a neutral pH, which can help balance out the pairings of both types when they are synthesizing proteins and regulating cell activity.


Alpha-keratins are the exclusive form of keratin found in humans and the wool of other mammals. The structure of the alpha-keratin is fibrous and helical, and both types I and II keratins can fall under the category of alpha.


Beta-keratins are categorized as polypeptide chains and are only found in birds and reptiles, although those species can also possess alpha-keratins. They have been a large contributor to the overall evolution of birds throughout history.

Both alpha and beta keratins help these animals maintain the composition of their claws, scales, beaks, skin, and feathers.

Structure and Function

The structure and function of keratin proteins are determined by their amino acid chains. These chains are very similar in species across the board. Humans share similar amino acid sequences with bovine species and rats.

Keratin cannot be dissolved in water, solvents, acids, or alkalines, so its structure remains largely intact when exposed to many of the body's chemicals. Keratin proteins rely on hydration (water) to maintain their overall size and function. To put this into context, wool is full of keratin. When a wool sweater is washed in heated water, it shrinks. This is because the keratin proteins lose their length when some of the molecular bonds break at high temperatures. 

Associated Conditions

Hyperkeratosis (excess keratin) can lead to a variety of different conditions.

Hyperkeratosis can develop due to inflammation. Pressure-related hyperkeratosis occurs when excess keratin is a protective response to skin damage, whereas non-pressure related keratosis happens without an identifiable reason and can be caused by genetics.

Conditions involving keratin include:

  • Keratosis pilaris (chicken skin): Although keratosis pilaris can have an unwanted appearance, it is not dangerous in any way. It happens when keratin clogs pores and blocks hair follicles.
  • Actinic keratosis: This skin condition causes lesions on the body that can feel like rough sandpaper. The lesions are considered a precursor to skin cancer, and your healthcare provider may monitor your skin and/or treat the lesions.
  • Epidermolytic hyperkeratosis: This form of hyperkeratosis is inherited, and it is present in infants at birth.
  • Lichen planus: This is a type of inflammatory disorder that most commonly affects the flexor (inner) surfaces of the arms and legs. It can be caused by an overproduction of keratin in the body.


Treatment of hyperkeratosis depends on the specific condition. For lichen planus, a corticosteroid cream may be prescribed by your healthcare provider, whereas you might need cryosurgery to remove the lesions of actinic keratosis. For hereditary conditions such as keratosis pilaris, there is no known cure.

Uses of Supplemental Keratin

Many industries have used keratin or other vitamin supplementations that promote production of keratin as a form of maintaining or improving hair, skin, and nail health. The beauty industry has advertised keratin as a way to combat damaged hair.

Hair Treatments and Products

Keratin is often a component in hair treatments that are used for shinier and stronger tresses. Depending on the type of keratin used, the results will vary widely. In the case of isolated animal keratin, results were found to be less efficient overall.


Biotin is a B vitamin that has also soared in popularity because it is said to have a positive impact on the body’s ability to synthesize proteins such as keratin, thus leading to healthier skin, hair, and nails.

Soluble Keratin

As previously mentioned, keratin is not an easily dissolvable protein. The manufacturing of a soluble form of the protein has been targeted towards athletes who wish to supplement their protein intake for athletic performance.

Risks and Side Effects

Although there is not a lot of evidence suggesting that using keratin by itself is dangerous to hair, skin, and nail health, the chemicals that may be added to keratin hair treatments can have adverse effects. Formaldehyde exposure has been a problem for those who use hair products with keratin regularly.

The use of formaldehyde in these products can then lead to health issues, including:

  • Itching and stinging eyes
  • Nose and throat irritation
  • An allergic reaction
  • Itchy skin with or without a rash
  • Scalp irritation that may present with burns or blisters
  • Mood changes
  • Hair loss and damage

Extended exposure to formaldehyde has also been shown to have carcinogenic (cancer-causing) effects.

A Word From Verywell

Since keratin is a naturally occurring protein in the body, using keratin supplements is not typically necessary. If you suffer from a type of hyperkeratosis, your dermatologist (skin healthcare provider) can make treatment recommendations that improve your condition.

It’s important to talk to your salon stylist and your healthcare provider if you are looking to get a supplemental keratin treatment for your hair. It may help in the short-term, but the long-term effects of some products could be damaging to your health.

Opting for keratin treatments that are free of unwanted chemicals and substances such as formaldehyde will give you the opportunity to improve hair health without adding any unnecessary risk to your overall health.

Frequently Asked Questions

  • What does keratin do?

    Keratin is a type of protein that maintains the health and structure of our hair, skin, and fingernails. For example, keratin affects hair texture, causing it to be straight, wavy, or curly.

  • What is hyperkeratosis?

    Hyperkeratosis is the excessive production of keratin proteins. It can be caused by inflammation as a response to skin damage, genetics, or for unknown reasons.

  • Are there side effects to keratin treatments for hair?

    Side effects of keratin treatments for hair can include coughing, wheezing, eye irritation, headache, dizziness, nausea, chest pain, vomiting, rashes, and more. High levels of repeated exposure have been linked to some cancers, including leukemia.

    These side effects are not caused by keratin itself, but instead by formaldehyde, a chemical used in certain keratin treatments for hair.

15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Angelica Bottaro
Angelica Bottaro is a professional freelance writer with over 5 years of experience. She has been educated in both psychology and journalism, and her dual education has given her the research and writing skills needed to deliver sound and engaging content in the health space.