The body's response to infection or inflammation is fever, which also serves as a defence mechanism against things like viruses and bacteria. The body releases molecules called cytokines into the bloodstream when it is infected or inflammatory. The blood-brain barrier, a system of microscopic blood vessels that shields the brain from potentially dangerous substances, cannot withstand the size of these molecules. Fever, however, is merely a symptom that materialises after the brain has sent out signals on its own.
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