Why Do Some People Develop Food Allergies Later in Life?


If you are an adult who has been recently diagnosed with a food allergy, then you know the struggles that accompany adult-onset food allergy. Previously, you were probably able to order just about anything from a menu or pick up any items from a grocery store shelf with minimal worry. Now you are faced with new challenges, like using an auto-injector. You also have learned about how to avoid foods that may cause you to go into anaphylaxis and may find yourself explaining to your questioning friends and family why you can longer eat certain foods. Some of your family members may even question you, saying it is not possible to develop food allergies later in life, after your immune system is well developed. They are wrong.

Although the majority of food allergies develop in children, it is possible for you to develop them later in life. The picture is not entirely clear yet as to why this happens, but some research studies are beginning to shed some light onto possible reasons.

More Adults Have Adult-Onset Food Allergy Than You May Think

Although the majority of research focuses on children’s food allergies, a sizeable portion of the adult population has them, too, at about 5 percent (compared with about 8 percent of adolescents). Some children may outgrow their food allergies, but many retain them into adulthood.

Few studies were previously led that focused on adult-onset food allergies, which is why Dr. Ruchi Gupta, food allergy researcher at the Ann and Robert H. Lurie Children’s Hospital of Chicago and Northwestern Feinberg School of Medicine, led a new, large study in 2014. Dr. Gupta said that anything you heard about adult-onset food allergy was anecdotal prior to this study. Researchers wanted to figure out how often this was happening and whether they could find any links.

Dr. Gupta and his colleagues from Northwestern University surveyed 40,447 adults. According to their research, nearly 52 percent of adults in the United States with reported food allergy developed their condition after the age of 18. Surprisingly, all of the Top 8 allergens (milk, egg, wheat, peanut, tree nuts, soy, fish and shellfish) were represented in their results. They found that the most common food allergen among adults was shellfish, affecting 3.9 percent of the U.S. population. Next in line were peanut allergies, which affected 2.4 percent, and tree nut allergies, falling in at 1.9 percent. Soy, milk and egg allergies were also evident, despite the fact that they were previously associated solely with childhood.

But How can Adults Develop Food Allergies Later in Life?

Many adults with newly diagnosed food allergies find that the foods they are now allergic to are foods they previously enjoyed and wonder what caused it, according to Dr. Gupta. What is it that triggers this switch to flip, causing a newfound allergic reaction in adults?

While some suggest their transfer happened as the result of pregnancy, the environment or an illness, conclusive evidence is still being sought out. But researchers have not come up empty handed.

The most common reason for individuals to develop food-related allergies beyond the first few years of life is due to the fact that something they become allergic to is related to something else they are allergic to. This pattern is known as oral allergy syndrome, which can occur in people who have seasonal allergies. For example, some people are allergic tree pollen. Some proteins found in tree pollen are similar to those found in some fruits and vegetables. When your body eats these foods in raw form, it thinks you are ingesting tree pollen.

A similar reaction can occur in people who are allergic to dust mites. Dust mites share similar proteins with shellfish, which can lead to the development of an allergy to shellfish in people who were previously only allergic to dust mites.

Although it is not yet clear what causes the development of a food allergy later in life, answers are slowly being unveiled.