Hives. Possibly the most common reaction is hives.
Rash/breathing diff. Immediate (minutes) and delayed reactions can arise from gelatin allergy. Immediate: hives, respiratory difficulty, throat swelling and low blood pressure. Delayed: a rash that appears 1-2 days after the exposure. Gelatin is found if food and meds/vaccines. Some people react only to food gelatin, others only to pharmaceutical. Kosher gelatin is made out of fish - no crossreact. To reg. Gelatin.