OuchThatHurts
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Your skin and eyes are red because your capillaries on the surface of your skin and in your eyes are dilated and so blood pressure decreases. Beta-blockers and many other BP meds work this way. Others add a diuretic which decreases blood volume also decreasing blood pressure. So you can make the capillaries bigger or make the blood less. Same net effect.Yes for sure. At least if only used sparingly. If taken on a daily basis, it isn't as bad after a few days. It also makes my skin and eyes red so I end up having to use eye drops (this does not go away for me). So it does come with some downsides.
There are many other factors at work like stress for example. When you're stressed adrenaline is released. Since it's a fight or flight hormone, it constricts capillaries so there is less blood loss from your attacker or opponent. Cold is similar as well. It constricts capillaries so most of your blood remains around your organs. Your body knows it can lose fingers and toes. It can't lose a liver or heart.
Vasocontrictors like caffeine, adrenaline, amphetamines, etc will raise blood pressure also.
Alcohol is a vasodilator. Ever notice the cold doesn't feel so cold when you've had a few? Like the St. Bernard with the mini-barrel of brandy around it's neck? Problem there. Yea alcohol will dilate your capillaries, but that just results in you losing heat that much faster. People have frozen to death coming off Mt. Everest because they had too many celebratory drinks at the summit and had no clue they were hypothermic. Whoops! Should have waited for base camp.
Based on what I just said, can anyone tell me why caffeine taken to help give you extra energy to get up a mountain, why it can kill you? Don't worry. This isn't a gotcha question. Just for fun. Anyone?