Sun Damage to Hair Explained -Summer Series pt 1

Summer will be here in the next few weeks, and that means more outdoor time! Most people will be applying their sunscreen on the skin religiously before they head out, but what about the hair? What kind of sun damage can we expect?

What the sun does to your hair

Research has shown that the protective lipids on the cuticles, and the cuticle membranes themselves get degraded after long exposure to sunlight. Visible radiation, UVA radiation and UVB radiation, all have a role to play in the damage the hair receives.[Additional Reference: Hoting, E.; Zimmerman, M. J. Soc. Cosmet. Chem. 48: 79–91 (1998).]

Sun light radiation attacks 4 things:

  1. Hair proteins. Light will travel to the cortex of the hair to a lesser extent. In most cases, the amino acids of the cuticle are altered to a greater extent than the amino acids of the cortex because the outer layers of the fiber receive higher intensities of radiation. But any part of the cortex that is exposed to the environment through a fissure will also be targeted.
  2. The cell membrane complex lipids. Those are found inside the cortex and between the cuticle layers. They cement the cuticles together holding them into place and helping them to lay flat. They also allow important ingredients including moisture to travel to the cortex of the hair. Research demonstrated how the cell membrane complex gets weakened from sun damage resulting in multiple fractures. [Read more about the hair structure here.]
  3. Hair pigments (such as melanin). Sunlight will cause the hair pigments to degrade and oxidize. Hair pigments protect the proteins of the hair by absorbing and filtering the impinging sun radiation and subsequently dissipating this energy as heat. However, in the process of protecting the hair proteins from light, the pigments are degraded or bleached. Dark hair is more resistant to photodegradation than light hair, because of the higher photostability (more resistant to light degradation) of eumelanin compared to pheomelanin. Often times you will notice that some areas of your hair has gone lighter in color when degradation takes place.
  4. The external protective lipid layer: The famous 18-MEA layers which protect the external cuticles also act as a barrier to seal in moisture in hair. They also help to keep hair pliable and soft. These get destroyed by sun damage.

Watch out if you have Chemically Treated hair

Research has also shown that those who have chemically altered hair are even more prone to sun damage. For instance the cell membrane complex lipids of chemically bleached hair are more readily degraded than the lipids of virgin hair. [ Reference: Hoting, E.; Zimmermann, M. J. Soc. Cosmet. Chem. 48: 79 (1998)]

Combinations of chemical treatments on hair often produce more than additive hair degradation. For instance, perming by itself produces less damage than perming + sun light exposure. Sunlight oxidation followed by peroxide bleaching is another example of a damaging combo.

Note that a few minutes of being outdoors at peak sun light hours will not significantly cause increased damage. The negative effects are observed after extended exposure: Think of how long it takes for you to get tanned.

If you have colored hair, well, sunlight can degrade the dyes over time making fading even quicker.

What does Sun damage translate to?

Sun damage will make hair more brittle to start with. The degraded proteins, the weakened cell membrane complex and the degraded pigments create a disruption in the rigid well structured keratin fiber. Increased porosity is noted as well as loss of mechanical strength in the fiber.

Eventually, the hair fibers suffer fissures/cracks in the cuticles. Hair breakage can become more prominent. The split ends become even more pronounced.

To the eye and touch this will translate to: hair that looks parched, looks dull (rough/misaligned cuticles), frizzy, tangled etc. The poor manageability also comes from the loss of lipids in the hair.


Hair should be protected from sun damage as much as the skin. In pt 2 of this summer series, we will discuss the ways that we can protect hair.

Originally published at on April 30, 2016.

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