According to a study released in 2013 by the Centers for Disease Control and Prevention, food allergies among children increased approximately 50 percent between 1997 and 2011. The number of people who have a food allergy is growing, but there is no clear answer as to why. Prevention of allergen exposure is our primary goal. Anaphylaxis is a sudden, sever, allergic reaction to a drug, foreign substance, toxin, insect sting, food, or animal serum. A reaction may be delayed as much as four hours after exposure and reoccur up to 24 hours later.