When you should skip it: You have any type of illness, but especially a stomach bug.

什么时候不该喝：在你生病的时候（不管什么病），尤其是肚子痛时更不能喝。

Why it makes you feel worse: The caffeine in coffee is a diuretic, so it can make you pee a lot and leave you dehydrated. That's bad news when you're battling a virus or other infection, since getting enough hydration helps your immune system fight more effectively, says Kristine Arthur, MD, an internist at Orange Coast Memorial Medical Center in Fountain Valley, California. Caffeine is even worse when you're dealing¹ with vomiting² or diarrhea, since both can cause you to lose fluid. Taking in extra caffeine on top of that will only make that dehydration³ worse. Plus, caffeine can actually stimulate⁴ the muscles in your digestive tract⁵ and make your diarrhea more intense, Dr. Arthur says.

为什么会让你的病情加重：咖啡中的咖啡因是利尿剂，所以你上厕所的次数会变多，从而会脱水。当你在与病毒或其它感染作斗争的时候，这可不是好消息，因为水分充足可使免疫系统更为有效，医学博士克里斯蒂娜·亚瑟说道，她也是加州方廷瓦利橘子海岸纪念医疗中心（Orange Coast Memorial Medical Center）的内科医生。当你呕吐或腹泻时，摄入咖啡因会使情况更糟，因为这两种病都会使体内水分流失。除此之外，摄入额外咖啡因会使脱水更严重。此外，咖啡因实际上会刺激消化道肌肉，从而使得腹泻更为严重，亚瑟医生说道。