Why do eyes water when yawning?
829322
1- During a yawn, there is a slight increase in pressure inside the skull (likely caused by slight increases in the amount of oxygen taken in during a deep yawn). This causes the cerebrospinal fluid (CSF), the fluid that surrounds the brain and flows through the brain's ventricle system, to be forced out faster than normal. That fluid enters the lachrymal (tear) system. That increase in fluid pushes out the tears.\n\n2 - the more simplistic reason may be that when you yawn you scrunch up a bunch of facial muscles. That causes the tear glands and ducts to be squished, forcing out some tears.\n\n\nTalks about yawning as well:\nhttp://en.wikipedia.org/wiki/Yawn#Causes_of_yawning
1170939
From what I've read, we are not sure exactly why that happens, but many doctors and scientist believe is is due to a mental reaction that sees a person yawn and believes you should do so as well.  Yawning is a response to a lack of oxygen in the brain under idle conditions, such as standing around or sitting in a chair.  So when you see someone yawn, your brain triggers a yawn to make sure you are also not starving your brain.
339257
Yeah, the previous answers are right - lack of oxygen to the brain.\n\nBut the big question is why are yawns contagious? Even experts don't know that.
378590
People yawn when the level of carbon dioxide in their blood is a little too high, this is bad and eventually can cause unconsciousness.  To stop this you yawn, yawning means you take in a big gulp of oxygen and expel carbon dioxide.  They are thought to be contagious because if I see you yawning my brain thinks.. uh oh there is too much carbon dioxide in this room that person is already feeling the effects, to protect myself I will yawn too!\n\nBy the way you also yawn if you're tired because you're breathing naturally slows which makes carbon dioxide build up more easily.  You will yawn when you are tired to expel this excess carbon dioxide!
1119312
Tears drain away from each eye along two channels marked by a tiny opening at the inner edge of each lid. The channels lead to the lacrimal sac at the side of the nose, which is why your nose runs when you cry. Yawning exerts pressure on the lacrimal sac causing normal tearing.\n\nIf you have excessive teary eyes (or they are tearing all the time), talk to your doctor about it. If it is just when you yawn or wind is in your eyes or you are crying, this is nothing to worry about.
414151
What's behind this mysterious epidemic of yawning? First, let's look at what a yawn is. Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. We know it's involuntary because we do it even before we are born. Research shows that 11-week-old fetuses yawn. \n\nThere are many parts of the body that are in action when you yawn. First, your mouth opens and jaw drops, allowing as much air to be taken in as possible. When you inhale, the air taken in is filling your lungs. Your abdominal muscles flex and your diaphragm is pushed down. The air you breath in expands the lungs to capacity and then some of the air is blown back out. \n\nWhile the dictionary tells us that yawning is caused by being fatigued, drowsy or bored, scientists are discovering that there is more to yawning than what most people think. Not much is known about why we yawn or if it serves any useful function, and very little research has been done on the subject. However, there are several theories about why we yawn. Here are the three most common theories: \n\n\nThe Physiological Theory -- Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to drawn in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a psychologist at the University of Maryland, Baltimore County, and a leading expert on yawning, has tested this theory. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning. \nThe Evolution Theory -- Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities. \nThe Boredom Theory -- In the dictionary, yawning is said to be caused by boredom, fatigue or drowsiness. Although we do tend to yawn when bored or tired, this theory doesn't explain why Olympic athletes yawn right before they compete in their event. It's doubtful that they are bored with the world watching them. \nThe simple truth is that even though humans have been yawning for possibly as long as they have existed, we have no clue as to why we do it. Maybe it serves some healthful purpose. It does cause us to draw in more air and our hearts to race faster than normal, but so does exercise. There's still much we don't understand about our own brains, so maybe yawning is triggered by some area of the brain we have yet to discover. We do know that yawning is not limited to man. Cats, dogs, even fish yawn, which leads us back to the idea that yawning is some form of communication. \n\nHave we provoked a yawn out of you yet? If we have, hopefully it's not out of boredom, but by the power of suggestion.
329034
We yawn because of a lack of Oxygen. Think about it: when you yawn more air comes in and sometimes after a yawn you feel rejuvenated for a little while. But this is contagious because if you yawn you are probably in an Oxygen-deprived environment and everyone around you is going through the same lack of Oxygen. And yawning is related to sleep because when you're asleep you're barely doing more than breathing, beating your heart and dreaming which doesn't take up much oxygen but you still get the same amount of oxygen as you would awake in the same room so there's more oxygen to relax your brain and mind and everything else that might be tired.
261027
Why is this the second most asked question on here?  If the guys would stop asking about the size of their "manhood", this would be number one!\n\nWhy we yawn when we see others yawning has baffled scientists for ages and a number of suggestions have been put forward to explain this phenomenon. What we do know is that yawning is an involuntary action- our brain does it without us thinking about it, even very young babies yawn showing that it's a built in action (Chimps do it too by the way). Just thinking about yawning can trigger the bit of the brain that causes a yawn. http://www.ratlab.co.uk/yawn.htm...\n\nMore theories can be found at the links below: \n\nhttp://www.world-science.net/exclusives/...\nhttp://www.yesmag.bc.ca/questions/yawn.h...
346467
Yawns are not contagious, its an urban legend. Watch 'Mythbusters' on the Discovery channel.
664075
Researchers aren't really sure. They seem to have pinpointed the initiation to a particular part of the brain, and speculate that it's a synchronized social reflex that may serve an evolutionary goal of greater tribal cohesiveness and mutual protection. See the referenced web page. I've noticed that it's not just other people yawning, but even reading the word 'yawn' that does it for me, even if I'm well oxygenated and wide awake!
1177906
Yawning is your body's attempt to get more oxygen.  When you are tired, your breathing tends to get more shallow, and your body tries to compensate by making you yawn - bringing in more oxygen.\n\nHere's some more information on yawning, and why it's "contagious".
56869
The answer is, no one really knows why yawning is "contagious". Or why we yawn at all. One popular explanation is that yawning allows you to get rid of too much carbon dioxide in your system and increase your oxygen supply. This was disproved by Dr. Robert Provine and his research team in 1987.\n\nNow scientists are wondering if yawning is from our deep past -- part of our evolutionary history. Did a yawn signal to the group that it was time for everyone to retire to the trees and snooze? Did a yawn signal that we were all feeling cozy and warm about each other? Did a yawn signal something more like, "Gee, I know how you're feeling, I feel that way too."
56870
The dictionary tells us that yawning is caused by being fatigued, drowsy or bored, scientists are discovering that there is more to yawning than what most people think. Not much is known about why we yawn or if it serves any useful function, and very little research has been done on the subject. However, there are several theories about why we yawn.\nThe Physiological Theory -- Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to drawn in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a psychologist at the University of Maryland, Baltimore County, and a leading expert on yawning, has tested this theory. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning. \nThe Evolution Theory -- Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities. \nThe Boredom Theory -- In the dictionary, yawning is said to be caused by boredom, fatigue or drowsiness. Although we do tend to yawn when bored or tired.
198710
When you yawn, you are attempting to take in as much air as possible, more oxygen gives more energy.  People in the immediate area are in competition for this air too and yawn as a response to retrieve air themselves
1036057
Eye boogers are dried tears.  Tears have a great deal of salt and protein in them (think about how you have to clean contact lenses), so when the water evaporates as you sleep without blinking to clear the tears down your ducts, it leaves behind the salt and protein.
757509
sometimes if your eyes are really dry, it stings when your eyes water,  you should put eye drops in them to water them up
3436
Tears drain away from each eye along two channels marked by a tiny opening at the inner edge of each lid. The channels lead to the lacrimal sac at the side of the nose, which is why your nose runs when you cry. Yawning exerts pressure on the lacrimal sac causing normal tearing.