Will a relatively large dose of caffeine bring out hives in someone prone to them? I get 1 or 2 after taking tyl w caff, but not w plain tyle tabs.

Unusual. I am not aware of anyone being allergic to caffeine. However if you have a condition known as cholinergic urticaria (small, red, and itchy bumps lasting for a few hours), one can postulate that the heightened stress response from excessive caffeine could trigger cholinergic urticaria. If the typenol with caffeien is in a capsule form, gelatin allergy is a consideration. Fillers in t/cod?