It seems like more people than ever have a food allergy these days, but a new study finds not everyone who thinks they have such an allergy actually does. Northwestern University researchers looked at two groups of study participants over the course of a year. Over 40,000 U.S. adults were asked if they had a food allergy and were questioned about their reactions and diagnosis. Then researchers assessed whether the reported allergy, whether diagnosed or not, was “convincing.” The results showed the most common “convincing” allergy was to shellfish (affecting 2.9% of the adults), with milk and peanuts coming in second and third, affecting 1.9% and 1.8% of adults, respectively. Study leader Ruchi Gupta adds, “There are so many adults out there who have a negative reaction to a food. It is really important to get a proper diagnosis so that they can really know is this something treatable like lactose intolerance, or is this a life-threatening food allergy that they need to be very careful with.” It’s important to note this study had some limitations, including the reliance on self-reported data.