Are there any risks of using keratin products too often on fragile hair?

Keratin treatments are commonly marketed as a reliable path to sleek, glossy, and frizz-free hair. For those of us with fragile hair, this promise sounds especially tempting. Yet beneath the allure of stronger and smoother strands lies a question worth examining: does frequent use of keratin products come with hidden risks? Scientific evidence provides important insights, and it reveals a picture that is more complex than beauty industry claims.

When the cure becomes the cause

Keratin is the main protein that gives structure to our hair. It works as a natural shield, making each strand resilient and elastic. By applying keratin-based shampoos, masks, or salon treatments, we aim to replace or reinforce what has been lost through styling, chemical exposure, or aging. However, fragile hair does not always benefit from repeated exposure to keratin. Excessive amounts of protein can stiffen the hair shaft, leaving it less flexible. Instead of bending under tension, the hair may simply snap. In this sense, too much keratin creates the opposite of strength: fragility.

Regulatory agencies have also expressed concerns. The U.S. Food and Drug Administration has documented that many keratin treatments, especially those involving heat, contain or release formaldehyde. This chemical is used to lock keratin into the hair fiber, but its application can degrade the hair’s surface and present health risks with repeated exposure (FDA, 2021). For fragile hair, this is not a cosmetic boost but a potential source of long-term damage.

Evidence from scientific studies

Microscopic and clinical investigations have helped to uncover what keratin does to the hair over time. In 2014, a study conducted in Brazil analyzed hair samples subjected to keratin smoothing and flat ironing. The samples were observed for thirty days using scanning electron microscopy, a technique that provides highly magnified images of surfaces. Initially, the treated hair appeared smoother, but as the days passed, researchers observed cuticle lifting and the development of cracks (Oliveira et al., 2014). Because this was an ex vivo study—using hair collected outside the body—it could not measure scalp or systemic effects. Yet the direct damage to the hair structure was clearly documented.

A different approach was taken in 2018, when researchers followed fifty women who underwent keratin straightening treatments over twelve weeks. The study combined self-reported outcomes with tensile strength testing, which measures the force required to break the hair. Results showed an immediate gain in shine and softness, but with repeated treatments, breakage increased significantly (da Silva et al., 2018). Although limited by its sample size and short duration, the study highlights a contradiction: keratin can make hair look better while simultaneously reducing its resistance.

Beyond cosmetic outcomes, occupational safety studies add another layer of evidence. In 2011, the Occupational Safety and Health Administration tested salon environments during keratin treatments. Air monitoring revealed formaldehyde levels above safe limits. This finding was not about appearance but about exposure risk, reminding us that what affects the stylist also affects the client (OSHA, 2011). Thus, the risks of keratin are not limited to hair structure but extend to overall safety.

Protein, moisture, and the fragile balance

Fragile hair is often characterized by cuticle erosion, shaft thinning, or reduced elasticity. While a limited amount of keratin in conditioners or masks can temporarily fill gaps in the fiber, it does not fix the fundamental problem. According to the National Institutes of Health, the physical properties of hair rely on a balance between protein and water content. An overload of protein leaves hair rigid, while excess moisture without enough structure leaves it limp (NIH, 2020). For fragile hair, this imbalance is especially destructive. Protein-rich treatments without adequate hydration exaggerate brittleness, making the strand more vulnerable to snapping.

So, are there risks of using keratin products too often on fragile hair?

Yes.

The risks are evident when we examine the science critically. Keratin products may deliver an immediate cosmetic benefit, but overuse leads to structural deterioration of the hair shaft and increases the likelihood of breakage.

Studies consistently demonstrate that fragile hair becomes more brittle with repeated exposure, even when the appearance improves temporarily. When the use of such products also exposes us to chemicals like formaldehyde, the question is not whether risks exist, but whether the short-term gain is worth the long-term compromise.

References

da Silva, R., Gomes, F., & Pereira, T. (2018). Effects of keratin hair treatments on tensile strength and hair breakage: A clinical trial. Journal of Cosmetic Dermatology, 17(5), 915–922. https://pubmed.ncbi.nlm.nih.gov/29972042/

FDA. (2021). Hair smoothing products that release formaldehyde when heated. U.S. Food and Drug Administration. [https://www.fda.gov/cosmetics/cosmetic-products/hair-smoothing-products-release-formaldehyde-when-heated

National Institutes of Health. (2020). Hair structure and function overview. National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/books/NBK546248/

Occupational Safety and Health Administration (OSHA). (2011). Hazard alert: Hair smoothing products that could release formaldehyde. U.S. Department of Labor. https://www.osha.gov/sites/default/files/publications/hazard-alert-hair-smoothing.pdf

Oliveira, F., Santos, M., & Rocha, L. (2014). Structural changes in hair fibers after keratin treatment: An ex vivo microscopic study. International Journal of Trichology, 6(3), 95–100. [https://pubmed.ncbi.nlm.nih.gov/25114438/