A few months ago I kept getting stomach flu symptoms. I couldn't figure out what was making me sick. I thought maybe I was catching something from the dog, cat, or the chickens we raise. However, I was constantly washing my hands. I then realized it was the coffee I was drinking every morning. To test my theory, I switched from morning coffee to morning tea (Black tea). My stomach flu symptoms stopped. This morning, without thinking about it, I drunk coffee. Half-way through the day, my "stomach flu" symptoms returned.
Is it possible to just be allergic to the coffee itself? I drink sodas and caffeinated teas often without issue. Why the sudden allergy to coffee? I've drunk it for years without it.