Americans typically associate food allergies with children, but new research suggests that nearly half of all food allergies begin during adulthood.

While children often have nut or shellfish allergies, more adults are reporting having serious allergic reactions. Since these allergies don’t become prevalent until adulthood, many people do not get tested for allergies, potentially putting themselves at risk of an allergic reaction.

Northwestern University researchers looking at the differences between allergies in children and adults developed a detailed survey that asked multiple questions about the person’s allergic reactions, whether they had an allergy diagnosis and what symptoms they experienced. They surveyed more than 40,000 people and the most common reported food allergy was to shellfish, with 4 percent saying they developed this allergy during adulthood. Peanut allergies and tree nuts were also commonly reported, at around 2 percent.

The researchers also found that among black, Asian and Hispanic adults, the risk of developing a food allergy was higher than for whites, specifically for shellfish and peanuts. The researchers are planning a new study of environmental and other possible triggers for the allergic reactions.

Undiagnosed adults often mistake a food allergy for a food intolerance. This prevents patients from getting treated for their allergies, and it may also lead to harmful allergic reactions. For this reason, it is recommended to see an allergist to be tested for suspected food allergies. An experienced allergist can provide proper treatment for the allergy and any associated symptoms.