Ultraviolet radiation from the sun, also referred to as UV radiation, is quite damaging to our skin. Unfortunately, this is more so than people might think. I have written this article so my readers can better understand the consequences of sun exposure. As you will see, although tanned skin may be considered socially desirable by many, there is definitely a price to pay!
It is helpful to first know the basic anatomy of the skin, although I'll keep this as simple as I can!
There are three layers to the skin:
- Epidermis: This is the outer surface layer and it is generally about the thickness of a sheet of paper. It contains cells called melanocytes which produce a brown pigment called melanin. Melanin is what gives our skin the familiar tanned look. Every individual has a natural amount of melanin which helps give their skin it's natural distinct coloration. When you are exposed to the sun, the melanocytes react to the sun's ultraviolet radiation and produce more melanin as a way to protect the skin from radiation damage.
- Dermis: This is the next layer beneath the epidermis. Although quite complex, some of the major components of the dermis are blood vessels, hair follicles, nerve endings, collagen, and elastin. This is the layer that primarily gives the skin it's substance, and youthful appearance.
- Subcutaneous: This layer is technically not actually skin, but rather it joins the skin to the deeper tissues with fibrous bands. It is also called the hypodermis. This layer generally contains fat cells, nerve endings, blood vessels, and hair follicles. We are not really concerned with this layer when considering UV damage to the skin.
The sun is constantly emitting electromagnetic radiation, most of which is blocked by various gases in our atmosphere, such as ozone. UV radiation is a part of this electromagnetic radiation which passes through the atmosphere and reaches us.
We commonly see the terms UVA and UVB used when referring to sunscreen lotions. These terms refer to specific types of UV radiation that reach us and affect our skin. Following are the important differences between the two.
- UVA: Most of the radiation that reaches us is UVA. It is a longer wavelength than UVB and therefore is able to penetrate the atmosphere, cloud cover, and window glass much more easily than the UVB. UVA radiation can easily penetrate our skin and reach the defect layer, the dermis, where it damages the collagen and elastin, and also indirectly leads to DNA damage through the production of free radicals. UVA does not cause sunburn so it is secretly causing damage without any immediate evidence such as a sunburn. In fact, the SPF rating of sunscreens only pertains to the blocking of UVB radiation.
- UVB: It is the UVB radiation that causes sunburn. UVB penetrates the skin, causing damage to collagen and elastin, and also causing direct DNA damage. It is this direct DNA damage that leads to what we know as a sunburn. UVB radiation does not penetrate glass. This can give a false sense of security since you will not get burned by sunlight passing through glass, and you may think you are not being affected by the sun. This is a terrible misconception, since the UVA radiation does pass through glass and it will harm your skin.
As I mentioned earlier, UVA and UVB both cause damage to our DNA, but they do that in different ways. UVA radiation indirectly causes DNA damage by producing free radicals which in turn damage DNA. UVB radiation directly causes DNA damage as it makes contact with the DNA. Much of the UVB that reaches our skin is safely converted into heat, but a fraction of it damages our DNA and causes sunburn. The damage to the DNA causes cell death, and rarely the dead skin peels off as is commonly seen following a sunburn.
I mentioned earlier that our skin produces melanin as a way of protecting our skin from sun damage. Our skin reacts to the attack by UVB radiation and boosts melanin production in an attempt to protect itself from the potential damage. This is because melanin absorbs UV radiation and dissipates it as heat, essentially neutralizing the UV radiation. Melanin is what gives our skin a tanned look. This additional melanin production is why exposure to the sun will give us a suntan.
A tan is actually a protective mechanism, and is evidence that damage has already been done. It takes a couple days for a suntan to develop because the body needs time to produce additional melanin. Although it is mainly the UVB rays that cause a sun tan, UVA rays can produce something of a quick but much shorter lasting tan by oxidizing the already existing melanin, so making it more noticeable.
Sunscreens do offer protection against the UVA and UVB radiation of the sun, but it has it's limitations, and there will still be some degree of damage to the skin. Sunscreens only work as intended when they coat the skin, and they lose their effectiveness when they absorb into the skin. When sunscreens absorb into the skin, they will still help prevent sunburn, but they can lead to deeper skin damage. Many studies have shown that UV radiation affects absorbed sunscreen through chemical reactions causing free radical production, which in turn leads to indirect DNA damage.
It is believed that this indirect DNA damage is one likely cause of the most deadly skin cancer, malignant melanoma. It is important to apply additional sunscreen before it wears off, so there is a good protective coating on the surface of the skin to help prevent the free radical production. The best protection is to generally stay out of the sun as much as you can, and wear protective clothing and a hat when you are in the sun.
The proteins collagen and elastin are very important components of our skin as far as maintaining a youthful appearance. Collagen gives our skin it's strength, durability, and endurance. Elastin gives our skin it's durability, allowing it to stretch and quickly return back to normal again. Photoaging is a term referring to the premature aging of our skin caused by the sun. It is well known in the scientific community that elastin is damaged by the sun. In fact, 'elastosis' is a condition referring to degenerative alterations of the elastin which are generally characteristic of photoaged skin. Wrinkled, sagging skin, may in large part be due to this damage to the elastin component.
One predominant way in which the collagen of our skin is damaged by the sun is in the over production of enzymes which break down collagen. The cells of our body are constantly replaced by new cells, and these enzymes play a role in this process. However, within hours of sun exposure, excessive amounts of these enzymes, called MMP's, are produced, thus accelerating the breakdown of the collagen.
In summary, the aging effect of UV radiation on our skin weakens it, and commonly leads to wrinkles, and sagging skin. Skin does age naturally even without sun exposure; However, it has been proven that the sun accelerates the aging process, and can also lead to skin cancers. It is the proteins collagen and elastin which give our skin it's durability, and its wrinkle free smoothness. When the collagen and elastin are damaged, the skin loses it's elasticity, consistency, and it becomes less durable. Wrinkles form in intolerable areas, and you can see the skin bunch up into a finely wrinkled bulge when you pinch it or push it to the side. As far as we know, damage to our collagen and elastin can not be reversed. Please remember this before spending much time unprotected in the sun!