You're new. Are you trying to curse in Twencen? I don't need food allergies.
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Bear in mind that I'm not a medical doctor.
A food allergy is where your body's immune system can see a certain type of food as a threat, and it will react accordingly. A person could have tingling in their mouth if they eat a certain thing, or they'd get hives. Or they might be sick, or there could be swelling around the face (around the eyes, lips, tongue and so on.) Usually it's pretty mild, but it can get quite serious and medical intervention would be required.
I think the most common food allergies are nuts, shellfish, gluten (found in wheat, barley and rye, so anything made with those sorts of flour counts), lactose (from milk, so anything that then derives from milk, like cheese, cream, butter etc) and eggs. Dr. Cuddy will know far better than I do, though.