Keratin is a protein found naturally in the human body that makes up physical structures such as the hair and nails. When these basic structures become weakened and keratin is lost, it is possible to add keratin through cosmetic processes to fill in gaps in the original keratin fibers, providing better strength. Most commonly, people use keratin as a hair straightening treatment. The possible keratin side effects include hair loss, allergic reactions, itching, rashes, irritation of the eyes, lungs, throat, mouth and nose, hair dryness, and cancer. These side effects are not from the keratin itself, but from the processing tools and additives included with the keratin products that help them work.
Some people who use keratin products find that, after a treatment, hair is extremely dry and brittle. In some cases, this leads to breakage and thinning of the hair. This happens because cosmetologists use heat-based styling tools such as flat irons to coax the hair straight. The heat saps the moisture from the strands and causes a loss of elasticity. The problem worsens as an individual continues to style the hair with heat-based tools, unless she is vigilant about using conditioning and moisturizing treatments.
Almost all of the other keratin side effects are due to the formaldehyde the products include. Formaldehyde helps hold the keratin molecules together, which is largely what makes the product effective. This chemical is a known carcinogen. Problems such as irritation of the throat and lungs come from inhaling the formaldehyde during processing. Experts recommend that keratin products have no more than 0.02 to 0.2 percent formaldehyde for this reason, but this is problematic because the treatment is not as effective with anything less than 2 percent, with many manufacturers making products with percentages as high as 10 percent.
Concerns about keratin side effects have led professional health agencies to crack down on companies that have unsafe levels of formaldehyde in their keratin products. In response, some manufacturers replace formaldehyde with other chemicals. These manufacturers can and do market these products as formaldehyde-free, but the products are not necessarily safer. Other manufacturers remove harmful ingredients, replacing them with plant-based ingredients to seal the keratin, but these wash out easily and sometimes lose their effectiveness after just one wash.
Despite concerns about keratin side effects, some individuals continue to use keratin products because of the convenience and beauty they believe is found with straighter hair. Many women, for example, can spend well over an hour trying to wash, blow-dry and iron kinks, curls and waves out of hair. With a keratin treatment, a person can sometimes finish styling in just a few minutes. Cosmetologists have greater risk for keratin side effects because they work with keratin products on a much more regular basis compared to their clients.