Food allergies can have serious health repercussions. An estimated 5.6 million children and adolescents suffer from a food allergy, according to new research in the journal Pediatrics, which was based on data from a nationally representative sample of 38,408 youths under age 18. And 1 out of 5 had been to the emergency room at least once in the previous year because of a severe allergic reaction. Peanuts rank as the most common food allergy, affecting about 1.6 million youths, followed by milk allergy, affecting 1.4 million. Other common allergens are shellfish, tree nuts, eggs, fin fish, wheat, soy and sesame. About 40 percent of the youths in the study were allergic to more than one food. Although sesame ranks as only the ninth most common allergen, 1 of every 3 kids with a sesame allergy had been to the ER in the previous year. Allergic reactions can range from mild to severe and may develop within minutes or not until a couple hours after the allergen has been consumed. Symptoms can include trouble breathing, stomach pain, itchy and watery eyes, hives, swelling, and lightheadedness, among others. The most severe reaction, a life-threatening response called anaphylaxis, can make it nearly impossible to breathe because the airway becomes swollen. Injecting the drug epinephrine counters that, which is why doctors urge anyone, young or old, who has a food allergy to always carry an auto-injector device containing the drug.