The input below is only a description of my symptoms, which may be irrelevant in your case.I have a number of food allergies, the most severe of which is a caffeine allergy. It only rears it's ugly head when I ingest a large enough dosage.For example, drinking one large mug of hot tea will typically produce IBS symptoms many hours later. Drinking less than that might not produce any symptoms at all.Ingesting a good sized cup of strong coffee will produce a very rapid reaction, which borders on anaphylactic shock: Clamminess, lightheadedness, palpitations, nausea, incipient loss of consciousness. The first time this happened it was severe enough I thought I might be having a heart attack. The only solution for me is complete avoidance.I don't know the ratio of caffeine in coffee to that in tea, but there is clearly a dosage beyond which I cannot go without risking a very bad reaction.If your symptoms are similar, it is possible you could have a severe allergy, but again, a doctor would be in a much better position to make this judgement.