I am not allergic to almonds but developed an itchy rash and upset stomach after drinking almond milk. must i be allergic to an additive?

Probably: Check the ingredient and have a chat with your doctor about it

Maybe: Might not be an allergy at all. Timing of symptoms and amount of almond milk ingested is important. Anyone else drink it and develop symptoms? One can develop new tree nut allergy in adulthood, but sensitivity to other ingredients is also possible. Skin testing has very good predictive value to see if you are, or aren't, sensitized.

Not clear.: You may be allergic to either almonds or to another ingredient in the milk, or it may just be a sensitivity to one of those components, without being an allergy. Your choices are to either just not drink almond milk, or to see an allergist to be tested. Good luck.