Everyone thinks they know what an allergic reaction looks like: red, itchy eyes and a runny nose that erupts within 20 minutes of entering a house with a cat; a scratchy mouth and throat after eating raw carrots; hives after taking a medicine. Triggered by anything from birch pollen to pet dander, peanuts to penicillin, more than 50 million people in the U.S. suffer from seasonal, indoor/outdoor, food, skin, and drug allergies every year.
As you’ll recall, an allergic reaction is an immune response in which the immune system mistakes a normally harmless antigen, such as a dust particle, as a threat and produces large numbers of IgE antibodies to combat it. When the immune system comes into contact with that antigen again, the IgE antibodies are ready and waiting to mount an attack, releasing histamines and other inflammatory molecules that can result in itchy or swollen eyes, drippy nose, asthma, rashes, and a host of other physical symptoms.
Food allergies are particularly common—it’s estimated that 5.6 million children in America have them (that’s about 8% or 1 in 13 kids). Eight foods are responsible for about 90% of food allergy reactions: milk, eggs, wheat, soy, tree nuts, peanuts, fish, and shellfish—with milk, eggs, and peanuts being the most common. However, just about any food can cause an allergic reaction.
And as it turns out, everyone doesn’t actually know what an allergic reaction looks like. In fact, some allergies don’t manifest with physical symptoms at all.