Michael Patella asked:
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.
Winston-Salem, NC USA
We posed this question to Cambridge Laboratory of Molecular Biology scientist Mick Hastings...
Mick - The bottom line is, no, but it is an intriguing question. Melanin is produced in response to light actually in the skin itself. It doesn’t come from any glands, but there is a gland called the pineal gland, not the pituitary gland, the pineal gland which produces something called melatonin. The interesting biology here is that melatonin can effect pigmentation of skin in amphibians. In fact, that's how it was discovered, but melatonin has no effect on the skin of humans. It’s actually melanin that makes us go darker in response to the sun.
There's still another neat piece of biology underlying this and that is to say that in recent years, what's been discovered is a completely novel set of light responsive cells in the retina called intrinsically photoreceptive retinal ganglion cells. They're nothing to do with enabling us to see the world around us, but they are there for us to sense changes in light intensity and quality.
These cells have a very important effect on our mood, on our biological clocks and our circadian rhythms. So at some level, if one were to wear sunglasses, it would affect not just how we see the world in terms of objects, movement and colour, it would also affect our response in terms of our mood, which would include heart rate, pupil contraction, things like this. So there are some subliminal effects of light on the body which will be influenced by wearing sunglasses but to cut to the chase, this will not affect whether or not we’re more or less sensitive to sunburn and sun tanning.
Sunburns are caused by overexposure to the sun by the skin. It is not caused by wearing sunglasses. widereader, Wed, 21st Dec 2011
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) Sprool, Wed, 11th Jan 2012
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. anya, Sat, 23rd Feb 2013
confusion between melanin and melatonin
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. techmind, Wed, 8th May 2013
I don't think reaction time is that fast, if it were instant, no one would burn. Peter the painter, Tue, 14th May 2013
Melanocyte stimulating hormone is produced by the pituitary hormone even though melanin itself is produced in the skin so it seems likely that there is some connection here. My educated guess is that higher levels of MSH due to stimulation of the pituitary gland by sunlight makes melanin production in the skin more efficient = less likely to burn. And of course you require too much exposure to sunlight as well as sunglasses to burn! I don't think anyone was suggesting that you will burn if you wear sunglasses inside or that if you stay in intense sun all day long that you will not burn as long as you wear sunglasses. (that was in response to an earlier post). Dawn, Mon, 24th Jun 2013
I think the real question with sunglasses is if it helps with INDOOR lighting - Does indoor lighting cause the MSH hormone to be produced through receiving the stimuli through the Eyes. Venie, Thu, 3rd Mar 2016