If you are someone who is struggling with and/or trying to overcome androgenic alopecia (AGA; pattern hair loss) you need to be very conscious of what is happening to your hair throughout the day. This is all due to the delicate nature of vellus hair.
Vellus hair is hair that is being negatively affected by the miniaturization process (the shortening of the growth cycle). They are the small, thin, colorless hair that, when you are suffering from AGA, slowly replace your healthy (terminal) hair.
Vellus hair develops over a long period of time. As the hair growth cycle becomes shorter and shorter over several years due to miniaturization, eventually vellus hairs get so short that they do not penetrate the surface of the scalp, to which the hair follicle is considered “dead”.
In order to be able to overcome hair loss you need to start using treatments before the vellus hair is dead, and any vellus hair that is still visible can potentially be regrown back into healthy hair. But recovering vellus hair takes much more than just using treatments, they are very delicate and you need to treat them as such otherwise you will never successfully regrow your hair.
Although there are many different factors that you need into account (learn more here), in this article we are going to be focusing on one in specific: sunlight and how it affects your hair.
How does sunlight affect hair?
Many people are misled into thinking that “the more sun the healthier your hair will be”, while this may partially be true, too much sunlight can do a lot of damage.
When your hair receives sunlight in small doses, the UV-B rays supply your hair and scalp with vitamin D which is very important for its health. Vitamin D deficiency and several types of hair loss have been shown to be correlated (1) and there is some evidence that it may aid in hair growth as well.
Essentially, ensuring that you have enough vitamin D is a good preventive measure to take to ensure that hair loss does not develop. So yes, a little bit of sunlight is actually very beneficial for the hair, but what happens if you are overexposed?
How sunlight can damage hair
Again, the vellus hairs are what you are trying to protect at all costs.
There are two types of UV rays that are emitted from the sun: UV-A rays and UV-B rays (which we already discussed), and when hair is overexposed to either of them problems can arise.
The first issue that may arise is that it can damage disulphide bonds in your hair. These are protein bonds that give hair its strength, elasticity, and hold the strands together. When these bonds become damaged the hair shaft becomes brittle and is much more likely to break, which can lead to thinning if it is prolonged. The hair may also dry out which exacerbates breakage and thinning.
Another way that sunlight can damage hair is by causing oxidative stress. Oxidation is a process that occurs normally in the body and has a range of functions, but oxidative stress occurs when there is an imbalance between antioxidants and free radicals.
Free radicals are molecules with unpaired electrons. They scrounge the body and steal electrons from other molecules which causes damage to cells. When this occurs in the scalp the hair cells can get damaged, which has been shown to cause premature graying and hair loss (2).
The last way that overexposure to sunlight significantly affects hair is by causing discoloration (3). This can be very detrimental for someone who is trying to regrow their hair.
One of the reasons that vellus hair looks extremely thin is because it is clear and discolored, and the last thing you want is for more hair to become discolored because it lets light shine through and exposes the scalp.
Although discoloration won’t necessarily decrease the number of hairs, it could severely worsen the appearance of thinning.
As you can see, you need to be acutely aware of how much sun exposure your hair gets if you are trying to overcome hair loss. From causing hair to become brittle, to discoloration, oxidative stress and more, too much sunlight will ensure that you have a tough time regrowing your hair.
But don’t forget about vitamin D.
In order to get the benefits of vitamin D without all of the negative side effects scientists say that 10-15 minutes of sun exposure/day is sufficient. You can also take a vitamin D supplement, but if you know you are going to be exposed to the sun longer than recommended make sure you plan for it otherwise you can kiss your hair growth goodbye.