Skip to content. Learn the signs and symptoms of food allergy. More than 50 million Americans have an allergy of some kind. You probably know one of those people or are one yourself.

In people with a food allergy, the immune system reacts to certain proteins in food as though they were harmful pathogens, such as bacteria, parasites, or viruses. The number of reported food allergies has increased in recent years. For instance, the prevalence of peanut allergy among children has reportedly doubled over 10 years in North America. Most food allergies develop in childhood, and children generally outgrow them, although this is not always the case. Food allergies can also develop in adulthood, but this is rarer. Not every person will experience all of the possible symptoms, and each reaction may be slightly different.

Back to Health A to Z. A food allergy is when the body's immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be very serious. Symptoms of a food allergy can affect different areas of the body at the same time.

Most people assume that a food allergy or intolerance is something you develop as a kid that may or may not stick with you throughout your life. But as it turns out, you can randomly develop food allergies as an adult, too. Yes, it's weird and totally disheartening—and it's also more common than you might expect.