Jun
25
2006

And don't wear sunglasses

in and

Sunbathers: Soaking up the sun in the California desert. Courtesy Mark Ryan.
Sunbathers: Soaking up the sun in the California desert. Courtesy Mark Ryan.

Here’s a question for the start of summer: why does exposure to the sun darken our skin but lighten our hair?

First let’s take a look at our skin. Human skin is the body’s largest organ, and acts as a barrier between our inner organs and the outside world. It’s made up of essentially two parts the epidermis and the dermis. The epidermis is the outer section and is comprised of a layer of living cells, topped by a layer of dead cells. The dead cells are the skin we see.

Even though the upper epidermis is just a lot of dead cells, it contains keratin, a tough protein that also makes up our hair and fingernails, Keratin is thicker on the bottoms of our feet and the palms of our hands for added protection against abrasions and other intrusions from the outside world.

Inside the dermis is where all the skin’s functioning equipment is located, These include nerves, sweat glands, hair follicles, blood vessels and special cells called melanocytes, which produce melanin, the material responsible for skin pigmentation, hair and eye color. Most humans have about the same amount of melanocytes, some just produce more melanin than others. Albinos, however, produce no melanin at all.

When our skin gets exposed to sunlight (particularly ultraviolet rays) melanocytes begin producing melanin to help protect the dermis, and keep the skin cells from getting fried. The melanin acts as an absorbing agent. So over time, as exposure to the sun continues, more melanin is produced and subsequently the skin becomes darker.

The hair is a different story. Hair color is also determined by melanin, but hair cells are dead, so sunlight doesn’t initiate melanin production but rather begins to break down the melanin already in the hair, and the hair’s color begins to fade or lighten.

Sunglasses may not be so cool: Courtesy Mark Ryan
Sunglasses may not be so cool: Courtesy Mark Ryan

I thought this last part was strange. The pituitary gland is tied to your optic nerve and is sensitive to sunlight. When light enters your eyes, it triggers your pituitary gland to produce a melanocyte-stimulating hormone (MSH) that activates your melanocytes to produce melanin. This means that wearing sunglasses can actually cause sunburn.

Your Comments, Thoughts, Questions, Ideas

Brooke Berkin's picture
Brooke Berkin says:

Can the bottoms of our feet and the palms of our hands get suntanned or sunburned?

Thanks,
Brooke

posted on Sat, 07/15/2006 - 7:25pm
R. A. King's picture
R. A. King says:

Some years ago I became very sensitive to what I finally deduced as ultra violet light produced by certain types of lighting in my workplace. One person described my symptoms as like sunstroke. What I also discovered was that by wearing UV protective goggles I could be exposed to ultra violet light without the ill effects. This seems contrary to your comment regarding the wearing of sun glasses. Can you explain the contradiction?

posted on Sun, 07/16/2006 - 11:23am
mdr's picture
mdr says:

Thanks for the insightful question Brooke. The bottoms of our feet and palms of our hands lack pigmentation (melanin), plus they're doubly thick to protect them, so I don't think it's likely that you can tan them. Burning them, however, is very possible. One of the places people (particularly darker-skinned ones) are recommended to regularly check for signs of skin cancer (including the potentially deadly melanoma) are the soles of their feet and palms of their hands.

posted on Sun, 07/16/2006 - 11:31am
Anonymous's picture
Anonymous says:

If you are a fair skinned person, almost always burn, is there anything you can do to increase your melanin? to darken your skin?

posted on Wed, 08/09/2006 - 12:32am
josey's picture
josey says:

no,nothing to be done - use self tanning creme/lotion. you are what you are - learn to live with it and appreciate it.

posted on Wed, 08/09/2006 - 2:20pm
Anonymous's picture
Anonymous says:

Is there a limit on how dark your skin will get with out accelerators? How long should it take to get rid of a farmers tan? And is two hours a day a few days a week enough to see a constatnt change?

posted on Thu, 04/05/2007 - 5:22am
Cale's picture
Cale says:

I'm from alaska and yes you can burn your palms, live 18 years in alaska then take a trip to hawaii and go snorkeling without and lotions and just shorts on sit in the water and sun for 3 hours.. turns out purple skin and white veins = painfully sunburned. out for 3 days.. no thanks.

posted on Sat, 11/17/2007 - 1:35pm
DO's picture
DO says:

Burned the top of my head once while shorkling i Akumal Mexico!

posted on Fri, 02/20/2009 - 3:10pm
mdr's picture
mdr says:

I snorkeled in Akumal, too, in beautiful Yal-ku Lagoon park at the north end of town. We went near the end of the day when the sun was just setting. It was beautiful - hardly anyone there. They didn't allow the use of suntan lotion there because it spoils the lagoon environment.

posted on Fri, 02/20/2009 - 3:25pm
DO's picture
DO says:

Last time I was there the water was very cloudy until you got close to the sea.
the times before it was very clear and full of fish.

posted on Fri, 02/20/2009 - 4:05pm
Anonymous's picture
Anonymous says:

your ending of your paper makes no sense. you have no bibliography to back this up and I cant say you are even remotely correct, in fact I don't believe it at all. Wearing sunglasses doe not cause cancer. you do not gain melanin through your eyes.

posted on Fri, 12/04/2009 - 2:11am
mdr's picture
mdr says:

Cancer? Where was cancer mentioned? You're obviously confusing 'melanin' - the pigment-creating compound produced in our body - with 'melanoma', the most dangerous of skin cancers.

posted on Fri, 12/04/2009 - 1:49pm
Jim's picture
Jim says:

That's amazing about the sunglasses but it can be difficult when it is really bright as they really do make it much easier to see lol.

posted on Thu, 01/21/2010 - 12:44pm
Anonymous's picture
Anonymous says:

I don't agree that we should go without sunglasses to prevent sunburn. As a fairskinned person, it doesn't matter if I wear sunglasses or not, I burn. I always burned as a child and never wore sunglasses then. The sun can and does cause damage to our eyes, including retinal damage.

I don't know if there is research about sunglasses reducing risk of sunburn though. And even if you are tanning, not burning, you are putting your skin at risk for skin cancer. Therefore, people should do their best to balance their time outdoors in the sun, which is important time for Vit D, exercise, fun, etc, and protecting themselves, sunglasses or not.

posted on Tue, 04/27/2010 - 12:56pm
FaithInTheBody's picture
FaithInTheBody says:

it makes sense that the human body is armed with a natural defence against sun rays, and that the eyes would be the first to sense light and tell your body to start adapting.

if you are fair skinned, your ancestry is probably not from a very sunny place, and you should limit sun exposure to whatever doesn't burn you.

posted on Sat, 01/12/2013 - 12:37am
bella451001's picture

does the MSH influence only the melenocytes of the eyes?? as much as i know pitutary gland have effect in all the body parts ...........
n wats with the sunglasses they reflect the sunlight instead of letting it in so how can it be dangerous to wear them???

posted on Tue, 04/27/2010 - 10:58pm
bella451001's picture

Hey so i know now we should buy only the branded sunglasses ...n avoid the others cause they are painted black due to which they absorb light n the branded ones are also coated with an other layer of something that reflect light:)

posted on Thu, 04/29/2010 - 9:07am
Anonymous's picture
Anonymous says:

Wow. You folks really don't understand this concept? Wearing sunglasses doesn't directly cause sunburn, no The do, however, cause the optic nerve to not signal to the pituitary gland that there are wicked UV rays around so it can then pass on the information to the body to produce more melanin to reduce the risk of sunburn. Sunglasses are a contributing factor. For fair skinned people who don't produce a lot of melanin it won't make much of a difference, you will still burn no matter what, but for people with darker skin tones who DO tan instead of burn, ditching the shades will make the process faster due to increased production of melanin that IS triggered by the optic nerve. Since the process is faster, it reduces the risk of burning because that protective tan is established faster.

posted on Fri, 06/18/2010 - 8:49pm

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