Why Do We Tan? Why Do We Sunburn?

(Last Updated On: July 19, 2019)
Why Do We Tan?

Many people have probably experienced the painful effects a sunburn at some point in their lives. This uncomfortable condition is the result of human skin being left exposed to the sun’s rays without proper coverage or protection. So the question is, what exactly is a sunburn and how does it happen? Well, in order to come up with an answer we have to start from square one. Let’s first look at why we tan. 

Sun Exposure and Your DNA

When human beings sit out in the sun, their skin is penetrated by ultraviolet radiation given off from the sun’s rays. As skin cells are penetrated their RNA and DNA is damaged. As you can probably guess, damage to our DNA is not a good thing. DNA is essentially the building block of our genetic profile, giving our bodies the essential instructions that it requires to develop and continue to survive. When DNA is damaged or altered by the sun’s rays, this can easily lead to skin cancer. 

Related post: What Is the Ozone Layer?

The good news is that the body has developed a natural solution to this common problem. Tanning is essentially the body’s inherent protection mechanism against DNA damage as a result of skin exposure. The body uses a skin pigment called melanin to reduce the number of UV rays that are actually able to penetrate the skin’s surface. People with darker skin tend to have higher levels of naturally occurring melanin.

Why Do We Tan?

This is all very interesting, but it doesn’t explain why people’s skin tends to turn a darker shade after increased sun exposure. This can all be explained by a process called melanogenesis, where the skin will begin to produce new melanin as a direct result of sun exposure. While a tan resulting from the darkening of existing melanin cells will tend to appear soon after sun exposure, extra pigment darkening resulting from melanogenesis will typically take longer to show up, often many hours after the actual sun exposure. In addition, UV radiation will naturally stimulate already existing melanin to darken in color. 

Where does all of that melanin come from? It is created by a special type of cell called a melanocyte. These unique skin cells generate melanin pigment and then push it out the cell toward the surface of the skin where it works to not only darken the skin into what we know as a tan but also convert all that extra UV energy into body heat. Talk about an efficient solution!

The final thing to understand is why skin tans will eventually tend to fade. If a person does not continue to expose themselves to UV radiation from the sun, the skin will naturally regenerate itself over time, pushing new skin cells up to the surface. Since there is no need to generate UV resistant cells anymore, these new skin cells will naturally have less melanin and cause the skin to return to a lighter shade. 

Why Do We Sunburn?

Why Do We Sunburn?

The more that the sun penetrates the skin, the more susceptible our skin becomes to permanent damage. This type of damage will manifest itself as what is known as a sunburn. However, unlike the name implies, sunburns are not the same type of burns as those thermal burns caused by touching something hot, like iron or exposure to fire. Sunburns are caused more specifically by a specific type of radiation given off by the sun called ultraviolet-B radiation

Essentially, while tanning is a relatively effective mechanism for warding off damage to skin cells caused by sun exposure, it will only work to a certain extent. If the skin is exposed to too much heat from the sun for too long, it will eventually burn, regardless of how much melanin it contains. That said, lighter skin will be more prone to this painful condition since it has less natural melanin to begin with. 

How Do Sunburns Work?

Once the body’s defenses are overwhelmed and the UV rays begin to damage the DNA cells, the body switches gears and goes into clean-up mode to try to fix the problem. The first thing that the body does is to increase blood flow toward the second most outer layer of the skin, which is referred to as the dermis. This extra blood flow helps the skin cells set about repairing the damage. But it also often causes a sensation of warmth, and gives the skin the characteristic red hue that we know as sunburn. 

Immune cells are also summoned to the site of damage, and will typically cause inflammation and pain as they do their thing to protect the damaged skin cells from invasion. However, pain isn’t always a bad thing, and the perception of discomfort tends to give the body the time it needs to heal. After all, the last thing that anybody experiencing a sunburn usually wants to do is head back into the sun. Within a few days, the damaged skin cells will begin to die off and this explains why sunburnt skin peels. 

Keep in mind that skin that has been sunburned will be more susceptible to damage in the future. So be sure to take note and ensure proper protection when enjoying all those warm days on the beach this summer!

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