[thedoc]

Hello,

I'd like to say thank you for your show.  I enjoy it thoroughly.

I have a question most of my friends laugh at.

I heard a while back that you are more likely to get sunburn if you are wearing sunglasses.  I have put the theory to the test and it has worked for me.  I didn't put on sunscreen or wear sunglasses, sun bathed for a few hours and I did not get sun burn.   Then I did not put on sunscreen and wore my sunglasses, had sun burn within a couple hours.   Of course I don't abuse this theory, I know eventually everyone will burn, especially fair skin . ( I am not fair skinned. )

I found some information on the internet: this link (quoted below) and then this one (more in depth).

*DO SUNGLASSES CAUSE SUNBURN?*

SKIN colour changes when you are exposed to the sun because your body is told to produce more melanin - skin pigment - by your pituitary gland.

Melanin stops your skin from absorbing ultraviolet light.

It is this ultraviolet light which has the effect of burning the skin.

But the pituitary gland only knows how much melanin to make from the signals it gets from the eye. If the eye says it's sunny, the pituitary gland goes into overdrive.

But with shades on, the gland is fooled so less melanin is produced - meaning a higher risk of burning.

With your access to some of the top brains in science, could prove or debunk this theory?  I know you probably have hundreds upon hundreds of questions coming to you weekly, so if you can't get to this question anytime soon I understand, but if you are able to address this, I would be grateful.

Thanks again for your great podcasts.  I have listened to other podcasts, but I have to say your ability to get "down to the brass tacks" makes your show a lot more enjoyable and informative.

Cheers,

-Michael Patella
Winston-Salem, NC USA

Asked by Michael Patella


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[CliffordK]

Interesting theory.

Darkening skin is usually due to local exposure to the sunlight, so if one wears T-Shirts all summer, one would get dark colored arms, but a light colored torso, or the "Farmer's Tan".

There may also be some effect with the eyes, but I would have to imagine that it would be a slow reacting effect, perhaps over a few days or weeks. 

If the theory is melanin production, then one should be able to document changes in protected areas (under clothing, watchbands, etc).  From personal experience, it seems as if these protected areas do not darken significantly in the summer, and are at risk if one wears shorts one day, but I haven't done any careful controlled experiments including avoiding darkening glasses.

Keep in mind, there are some notes that serious eye problems such as cataracts may be caused by sun and UV exposure.  There may be a long-term benefit for the eyes from wearing sunglasses.

[widereader]

Sunburns are caused by overexposure to the sun by the skin.  It is not caused by wearing sunglasses. 

[Sprool]

If your theory were true, then the act of closing your eyes would bring on sunburn, and skin would burn whether if it was covered up or exposed. This is clearly not the case. Skin cell melanocyte manufacture of melanin via the tyrosinase enzyme is well documented, and in response to UV radiation. The UV-A radiation component causes photodegradation of the skin whereas the UV-B  causes the burning damage. The skins natural response is to manufacture more melanin which is the skins natural UV absorbing protector. It is accompanied by a darker pigmentation - this is the suntan observed. (as opposed to redness when sunburnt which is tissue damage and subsequent inflammation)

[anya]

I have certainly noticed that I burn more quickly when I sleep in the sun (and therefore my eyes are closed) or when I wear sunglasses. In the book Survival of the Sickest, by Sharon Moalem and Jonathan Prince, on page 53 and 54, it explains that when less sunlight reaches the optic nerve, less melanin is produced and sunburn is more likely.

[RD]

confusion between melanin and melatonin

[techmind]

It could be more harmful to the eyes to wear sunglasses than not *if* they are poor sunglasses which cut the visible light (making the pupils dilate somewhat) but don't block the harmful UV to the eyes very much.

[Peter the painter]

I don't think reaction time is that fast, if it were instant, no one would burn.