It's interesting that you mention coffee, because after many long years of being a heavy consumer of coffee, I have now developed an annoying adverse reaction to it in the form of persistant angry red sore that regularly broke on my chin whenever I consume more than about 3 or 4 cups a day. At one time I was regularly drinking up to 6-8 coffees a day.
Another issue I had because of drinking too much coffee was persistant perspiration, which immediately went away when I moved over to drinking mainly tea instead. Although caffeine is also present in tea it only contains about 25% of the caffeine that coffee does. But seriously, coffee is'nt particularly healthy stuff if you are into drinking too much of it.
Obviously, I also had a very disrupted sleep pattern.