Coffee is an addicting beverage. If you consume more than 2 cups per day, you are likely to experience unpleasant withdrawal if you stop. The minimal suffering includes a headache, irritability, and fatigue. The popular idea that the bad effects of coffee are caused by one chemical, caffeine, is misleading. Coffee is also a crop with high pesticide residues.
Coffee is definitely allergenic and makes some people obviously sick.
Chlorogenic acid is one of the allergens which coffee shares with oranges. Black Tea and coffee have much in common, although they different plant products from different geographic zones. Tea contains caffeine and other members of the drug family, methyxanthines. Tea also contains tannin, a good tanning agent. The caffeine dose in a cup of coffee ranges from 100 to 160 mg.