Hi there, though I have not heard about having cravings because they might be allergic to certain food. I mean if they are allergic to the stuff and they ingest it, it could be life-threatening! If what your doctor means is a huge craving of some food before the patient develops that food allergy, it might be that way. But certainly not already allergic to the food and have huge cravings for it.
It is possible for a person to develop an allergy suddenly if they have never in their life have any before.
If a person is allergic to nuts, it can be very life-threatening! Sometimes just by kissing someone who has eaten peanuts and you are allergic to it, you can end up in shock! I'll see if I can find anything about cravings and allergy. Just my 2-cents...