19 percent of the nationally representative group reported having a food allergy. But only 10.8 percent said they had symptoms consistent with an allergic reaction to food, such as hives, swelling of the lips or throat, and chest pain. The main culprits behind these allergies were shellfish, milk, and tree nuts. Those who didn’t have a convincing food allergy instead reported symptoms like stomach cramps, a stuffy nose, or nausea. The findings, published Friday in JAMA Network Open, roughly match up to estimates from other studies, including those that confirmed a person’s food allergy with testing or medical records. In...