Dr. Anna Wolfson says she sees dangerous misuse of the allergy medication diphenhydramine in her clinic every day. “If someone has an allergic reaction to a food, people will say, ‘Don’t worry, I have diphenhydramine in my purse,’ and I would say, ‘Really, epinephrine is the first-line treatment for food allergies,’” said Wolfson, an allergist at Massachusetts General Hospital. Diphenhydramine can be harmful if people take it after having an allergic reaction to food, she said, because the drug – best known by the brand name Benadryl – makes them drowsy and can cause them to miss signs that their...