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Hair Photobleaching: How It Happens & How to Prevent It

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Table of Contents

Image of Black woman with back of hair facing the sun.

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Summer is synonymous with beach outings, pool gatherings, and, surprisingly, hair photobleaching. Yes, amidst the fun under the sun, your hair might be undergoing an unwanted transformation without your notice.

Hair photobleaching is a phenomenon where light radiation, particularly from the sun, lightens the color of human hair fibers, leading to a bleached look and a paler shade overall. While it might sound like a natural highlighting service, it’s actually a sign your hair is crying out for protection.

To explore this topic further and equip you with strategies to shield your locks from the harsh effects of the sun, I’ve sought the guidance of a hair scientist and cosmetic formulator with a PhD in Chemistry. This article will share his expert insights into the science behind hair photobleaching, its implications, and preventative measures.

What Exactly is Hair Photobleaching?

Image of Loose red hair in the sun.

Photobleaching refers to the process of using light radiation to lighten the color of human hair fibers. This process results in a bleached appearance and a lighter overall color tone.1,2

Hair color can change through photobleaching, which can be controlled or happen naturally. Controlled photobleaching can be used to alter the hair color shade, while natural photobleaching happens over time with repeated exposure to sunlight.

During the hot summer months, you may have noticed a change in the tone of your hair color. This is caused by the interaction of solar radiation with the fibers of your hair.

Which type of radiation causes more damage to hair color? Additionally, what are the other physical or chemical changes that occur during photobleaching, and how do they affect hair health, its properties, and cosmetic appearance? Let’s find out.

Melanin: Hair Coloring Pigment

Vector illustration - In cross section straight hair is round and curly is flatten. Black hair has mostly eumelanin, blonde has more pheomelanin. Grey hair has no pigment and has air in the medulla.

Hair color is due to melanin granules present inside the hair cortex (the same melanin that gives color to our skin). These gains are small sac-like structures lying inside the hair protein matrix.

The color of the hair fiber is created by melanin reflecting the visible light (400-800nm) in the solar electromagnetic spectrum. This means that the human eye can only perceive colors that are created through the reflection of visible light.3

To change hair color, two methods are commonly used: one involves bleaching the melanin using an alkaline hydrogen peroxide solution, while the other uses a light source emitting visible light radiation with a specific wavelength and energy to lighten the hair.

The energy of incoming light radiation must be high enough to break the chemical bonding of the melanin structure. This can be achieved by bombarding visible light radiation of a specific energy and bandwidth (wavelength) targeting melanin structure.2,4

In addition to bleaching melanin grains, exposure to solar radiation can cause other reactions. This is because solar radiation comprises a mixture of different wavelengths and energy, including high-energy UV radiation that can damage hair proteins and lipids.5

Why Hair Photobleaching Happens

Human hair fibers get their color from a complex and large polymer called melanin. Two types of melanin contribute to hair color – Pheomelanin and Eumelanin.

These types have unique chemical structures, which lead to different color shades. Eumelanin is responsible for black and brown shades, while pheomelanin imparts red to yellow shades in the hair.66 

The light from the sun penetrates the outermost layer of the hair, called the cuticle, and into the hair shaft. The protein in hair, called keratin, does not absorb this light, so it goes deep inside the hair fibers and is reflected by melanin grains.

Repeated and continuous exposure to solar radiation, including visible and UV light ranging from 200-800nm, can cause the breakdown and chemical degradation of melanin molecules. This results in a decrease in the overall concentration of melanin grains, causing a lightening of the hair color shade.

Under direct sunlight, two types of melanin exhibit different behaviors during photobleaching due to their varying chemical structures and response to UV and visible light. This chemical reaction is permanent and irreversible, resulting in a lighter hair color appearance, often with a more yellowish tint.

Why Is Hair Photobleaching Bad?

Image of side profile of curly haired woman outside in the sun wearing a black jacket.

Melanin, which gives color to our skin and hair, also acts as a natural antioxidant and protects our skin and hair from harmful UV radiation.

When hair is photobleached, the melanin grains are also bleached, causing it to lose its natural antioxidant. This makes it susceptible to oxidation caused by high-energy UV radiation. Numerous scientific studies have revealed that UV exposure can harm hair fibers.7

The UV radiation in the range of 200 to 400 nanometers in the solar electromagnetic spectrum is capable of breaking the chemical bonds of keratin.

Exposure of hair fibers to UV irradiation has shown high amounts of cystic acid, an oxidized product of cystine amino acids. This process makes the hair more hydrophilic, alters the electrostatic properties of the hair fiber, and increases hair porosity, leading to significant frizz. As a result, managing and styling photodamaged hair becomes challenging.

To put it simply, photobleaching can have adverse effects on hair. It can make hair weak, porous, frizzy, and dull.

How to Prevent Photobleaching

To prevent photobleaching and protect hair from its harmful consequences, follow these basic steps:

● To avoid hair damage, it is important to limit its exposure to sunlight. The longer the exposure, the weaker the hair becomes. If you spend a lot of time outside, it is recommended to wear a hat to reduce the duration of exposure.

● There are two types of sunscreen agents – physical sunscreen agents and chemical sunscreen agents. In hair care, chemical sunscreen agents are typically preferred because they are easier to apply to hair shafts and can absorb UV radiation to protect the hair and minimize damage.

Leave-in conditioner containing a blend of natural oils (e.g. olive oil, apricot kernel oil, grapeseed oil, etc.) also offers good protection against UV radiation. These oils are rich in vitamin E which has an excellent profile in controlling the photo-induced damage to hair and skin.

● To protect against UV damage, look for hair care products that contain natural extracts, such as green tea extract. This extract contains polyphenols that can reduce the impact of UV radiation by neutralizing free radicals. When shopping for hair products, search for rinse-off or leave-in conditioners that contain these extracts.8,9

Alternatives to Hair Photobleaching

Certain important factors must be considered to achieve the desired results when lightening hair color through photobleaching. First, only visible light should be used to prevent any damage to the hair fiber from UV rays.

Second, the bleaching process should specifically target melanin grains in the hair and should not oxidize the protein components of the hair structure. This can be achieved through visible light irradiation at a specific wavelength.

Melanin bleaching with alkaline hydrogen peroxide is a common method for managing the negative effects and limitations of photobleaching. Bleaching hair with alkaline hydrogen peroxide is a convenient and easy way for consumers to do it themselves at home or a salon. However, this process can weaken the hair structure and cause significant damage to the hair fibers.


Photobleaching is a process that uses light to lighten hair color and break down melanin granules. When exposed to sunlight, photobleaching can break down the structure of melanin, resulting in lighter hair color.

However, direct exposure to sunlight can cause photobleaching, which in turn can lead to the oxidation of keratin components, ultimately damaging the hair’s mechanical strength. To preserve the integrity of the hair fibers, it is recommended to limit your exposure to solar light.

Managing and styling hair fibers that have been damaged by exposure to light (photodamage) can be challenging.

One alternative method for lightening hair color is through the use of alkaline hydrogen peroxide. Regardless of which bleaching method is used, it is important to regularly condition, hydrate and moisturize hair fibers to ensure good quality, fiber health, and maintain a natural appearance.


  1. Dunford, R. L. The photo-assisted bleaching of synthetic melanins and hair. University of Keele, 1996. ↩︎
  2. Takahashi, T.; Nakamura, K., A study of the photolightening mechanism of red hair with visible and ultraviolet light: Comparison with blond hair. J. Cosmet. Sci. 2005, 56 (1), 47-56. ↩︎
  3. Zavik, C.; Milliquent, J., Hair Structure, Function, and Physicochemical Properties In The Science of Hair Care, 2nd ed.; Bouillon, C.; Wilkison, J., Eds. Taylor & Francis Group, LLC: London, 2005; pp 29-35. ↩︎
  4. Hoting, E.; Zimmermann, M.; Höcker, H., Photochemical alterations in human hair. II: Analysis of melanin. J. Soc. Cosmet. Chem. 1995, 46 (4), 181-190. ↩︎
  5. Nogueira, A. C. S.; Dicelio, L. E.; Joekes, I., About photo-damage of human hair. Photochem. Photobiol. Sci. 2006, 5 (2), 165-169. ↩︎
  6. Zviak, C., The Science of Hair Care. Taylor & Francis: 2005. ↩︎
  7. Hoting, E.; Zimmermann, M.; Hilterhaus-Bong, S., Photochemical alterations in human hair. I: Artificial irradiation and investigations of hair proteins. J. Soc. Cosmet. Chem. 1995, 46 (2), 85-99. ↩︎
  8. Davis, S. L.; Marsh, J. M.; Kelly, C. P.; Li, L.; Tansky, C. S.; Fang, R.; Simmonds, M. S. J., Protection of hair from damage induced by ultraviolet irradiation using tea (Camellia sinensis) extracts. Journal of Cosmetic Dermatology 2022, 21 (5), 2246-2254. ↩︎
  9. Marsh, J. M.; Davis, S. L.; Fang, R.; Simmonds, M. S.; Groves, P.; Chechik, V., UV Oxidation: Mechanistic Insights Using a Model System. J. Cosmet. Sci. 2021, 72, 697-710. ↩︎


I’m just a girl who transformed her severely damaged hair into healthy hair. I adore the simplicity of a simple hair care routine, the richness of diverse textures, and the joy of sharing my journey from the comfort of my space.

My mission? To empower others with the tools to restore, and maintain healthy hair, and celebrate the hair they were born with!

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