|MadSci Network: General Biology|
Why does blood in the stomach cause vomiting? The answer is...no one knows for sure. The best guess is that something about blood irritates the stomach. This is just about the same thing as saying, "We don't know." Though I am not certain about this, I suspect that the question has never been thoroughly studied. If it had been, a series of well-designed experiments could probably have isolated the substance or substances in blood that cause the reaction. There may be a Nobel Prize here somewhere. On another level, it does seem very strange that such an integral part of our body as blood could cause such an adverse reaction when placed within the stomach. There are precedents for this kind of thing, though. Rattlesnakes, for example, are not immune to their own venom; if they are bitten by another rattlesnake -- or if they were to bite themselves -- they would die.
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