There is a light pollution movement that says lighting at night obstructs melatonin production. They say:

What makes you fall asleep are changes in the level of the hormone melatonin circulating in your body. During the day, light stimulates a part of the brain. This brain part (known as the suprachiasmatic nucleus) tells the pineal gland to decrease the melatonin level when it is light out and to increase it when it is dark. The brighter the light, the bigger the decrease and the darker the dark, the bigger the increase of melatonin. By making your days lighter and your nights darker, you can improve both the quality of your sleep and the amount of time it takes you to fall asleep.

and recommend all kind of protection against the light,

Dark Nights: Make your nights as dark as possible. Draw the curtains, close the shades and keep the lights off. Try a sleep mask if you can’t get eliminate enough light. The darker your night, the quicker you will fall asleep.

Do I sense the light by the whole skin surface or only open eyes? If you sense by eyes, which are closed during the sleep, then what is the problem?

In other words, the question is: is the sleep mask sufficient for melatonin secretion or you need to cover the skin?

update What if I close only one eye? I tend to do this when the blinding sun shines. Does such light eject melatonin?

  • $\begingroup$ Close your eyes and look at a bright light. Close your eyes in a dark room. See the difference? $\endgroup$ – Nick Jul 29 '13 at 10:15
  • $\begingroup$ Do they give any reference whatsoever about that (I mean improving sleep quality etc)? $\endgroup$ – nico Jul 29 '13 at 10:51
  • $\begingroup$ So, the question is: is the sleep mask sufficient for melatonin secretion or you need to cover the skin? $\endgroup$ – Val Jul 29 '13 at 11:14

The release of the hormone melatonin is responsible for the feeling of sleepiness. It is released by the pineal gland and production starts when the light fades, as it's production is inhibited by light stimulation of the retina, the onset of the production is called dim-light melatonin onset.

Read more about this at this previous answer.

This study on blind people will show you that the light entering the eyes is the (main at least) regulator of melatonin rhythms. They took blind people, 19 of whom could perceive light and 30 who could not, and showed that 14 of 19 light perceivers had normal melatonin rhythms while 23 of the light-blind people had abnormal or unclassifiable rhythms.

  • $\begingroup$ Do you mean that the skin surface is not responsible? Then, why do they recommend the face mask only as the last resort? Why do they want the lights off in the first place? $\endgroup$ – Val Jul 29 '13 at 12:10
  • $\begingroup$ @Val The quotes you put don't recommend "an eye mask as the last resort," but I assume the more you do the more light you can prevent the better - living here in Sweden I can tell you that blinds and curtains being closed and lights being switched off does not mean you will get darkness during the summer nights - an eye mask is a very effective measure. $\endgroup$ – rg255 Jul 29 '13 at 14:22
  • $\begingroup$ @Val I've also added a little about an interesting study on blindness and melatonin production $\endgroup$ – rg255 Jul 29 '13 at 14:34

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