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A hickey can cause the blood to raise to the top levels of skin, leaving you violet mark on the skin. However, articles about space exposure (Wikipedia, nasa.gov) do not talk about bleeding at all.

So does the blood slowly leak when you happen to be in the vacuum environment, or not? And if not, how come you can suffer such effect with much higher pressure?

I always imagine a man that survived vacuum exposure to be all purple-brown.

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    $\begingroup$ Before kids get a wrong impression of how kissing a woman feels like, what you're referring to is colloquially known as a hickey. It's also known under other names, but those bruise marks of blood cells trapping between the dermis and epidermis due to suction are not a consequence of a normal kiss. Kids will learn more about those as they grow up, but it should be also noted that bleeding due to a hickey isn't normal. ;) $\endgroup$
    – TildalWave
    Commented Jan 21, 2014 at 23:41
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    $\begingroup$ Well, I didn't mean literally bleeding, and I wasn't talking about normal good-bye kiss. $\endgroup$
    – Tomáš Zato
    Commented Jan 21, 2014 at 23:44
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    $\begingroup$ I realize that, but some might get a wrong impression, since you didn't really mention that in your question. ;) Anyway, here are related question: Reaction to taking a glove off in space and Puncturing space suit during EVA. What would happen? It would also help if you describe which parts of the body are exposed to vacuum, how big of an area and for how long. In particular, if the astronaut has a helmet on, since I can imagine all kinds of "picturesque" consequences of rapid depressurisation in that area... $\endgroup$
    – TildalWave
    Commented Jan 21, 2014 at 23:49
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    $\begingroup$ Is a woman kiss any different from other kisses? $\endgroup$
    – gerrit
    Commented Jan 22, 2014 at 11:37
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    $\begingroup$ Not sure, I never experienced man's kiss. If I knew you guys will get so shocked by using this a little exaggerated example, I'd really formulate the question differently. $\endgroup$
    – Tomáš Zato
    Commented Jan 22, 2014 at 12:33

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Vacuum on the skin will not normally cause blood to flow through the skin. It can cause the skin to distend (push outward) from the fluid pressure behind it, and to stretch the capillaries under the skin.

Actual vacuum exposures have shown that even 20-30 minutes of exposure do not result in external bleeding - but they do result in massive bruising. Joseph Kittinger was exposed to near vacuum for an extended period due to a lost glove during his "skydive from space"; his hand swelled, and he had bruising upon return to surface, but did not lose blood through the skin. It took 3 hours for his hand to recover to functional.

It is possible that extremely dry skin could crack and bleed from the distention caused by vacuum. This has not been seen in the handful of known vacuum exposures.

Loss of moisture through the eyes, mucus membranes, and lungs are more concerning. Likewise, the very thin membrane of the lining of the nose is much easier to penetrate, and so vacuum exposure could cause nosebleed much more easily than skin surface exposure.

Accordining to the Wikipedia entry, 6 people have suffered high quality vacuum exposure - counting Kittinger - and of them, the three fatalities were Soyuz 11's 3-man crew, who were depressurized for an extended period during reentry.

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    $\begingroup$ Good to have you back, aramis! $\endgroup$
    – called2voyage ♦
    Commented Jan 22, 2014 at 16:47
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    $\begingroup$ From what I have seen, the biggest problem is the very rapid onset of unconsciousness. Under very low pressure or vacuum oxygen will rapidly diffuse OUT of the blood and into the lungs. 15 seconds is an outer limit. In the last 15 years there have been a couple of private jets that lost pressurization while climbing to cruise altitude and the pilots did not even have time to grab the oxygen mask that is in easy reach. Could you hold a partial breath that prevents blacking out without an embolism? Good question. It works in SciFi. Nobody blows up like in the movies. $\endgroup$
    – C. Towne Springer
    Commented Jan 23, 2014 at 8:50
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    $\begingroup$ Correction: Joseph Kittingers glove got depressurised — he did not lose it completely. If you jump down from 30 km with a missing glove, I'd guess the fingers will fall off due to freezing. $\endgroup$
    – gerrit
    Commented Jan 29, 2014 at 11:59
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I read an article on Soyuz 11. Kind of relates to your question. Due to depressurization, crew of Soyuz 11 died. The statement given by the chair of state commission was:

Outwardly, there was no damage whatsoever. They knocked on the side, but there was no response from within. On opening the hatch, they found all three men in their couches,motionless, with dark-blue patches on their faces and trails of blood from their noses and ears. They removed them from the descent module.Dobrovolski was still warm. The doctors gave artificial respiration. Based on their reports, the cause of death was suffocation...

Source: Wikipedia on Soyuz 11

Another article on Space.com also has a list of space hazards involving fatalities.

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    $\begingroup$ That Wikipedia article on Soyuz 11 actually quotes an article from Space Safety Magazine that is a lot more informative. Don't get me wrong, quoting from Wikipedia is fine, if it's attributed and all other things taken care of that are required when extracting information from external sources. But, at the end of the day, such Wikipedia pages are little more than collections of quotes themselves, so it might be worth following references they list. ;) $\endgroup$
    – TildalWave
    Commented Jan 24, 2014 at 22:58

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