Can I Develop Food Allergies as an Adult?

Is there any research or data on food allergy development throughout life? I often hear of individuals who develop food allergies (not just sensitivities) as adults. If a baby/child does not show any symptoms of food allergy, is there a chance it could develop later, and do we need regular exposure to prevent it?
—Kate

Adult-onset allergies do occur, although they are both much less frequent and much less consistent.

(If you want to dive really deeply, this article is extremely comprehensive [and long!]. I relied on it but will try to be more concise.)

With kids, about 90% of allergies are made up of the top 8 causes (milk, eggs, wheat, soy, tree nuts, peanuts, fish, shellfish). Eggs, milk, and peanuts are the most common causes. Many of these allergies actually disappear as children age — eggs, milk, wheat, and soy are all sensitivities that kids commonly shake as they get older. And of course, as I have discussed before, early exposure can limit the development of these conditions.

I realize this wasn’t your question, but it is a useful place to set the stage because, first, it illustrates that in general, allergy rates go down rather than up with age. And, second, it provides a frame for the way in which adult-onset and childhood-onset allergies tend to differ. Mainly, childhood allergies are a lot simpler. Most childhood-onset allergies are a result of primary sensitization — meaning it is just the culprit food the child is allergic to.

In adult-onset cases, the situation is often more complicated. One complication involves pollen. Adults often develop pollen sensitivity. This is the primary sensitization, but sometimes it cross-reacts with particular foods. This can result in a loss of tolerance to the food, even though the primary issue is the pollen. These pollen-mediated allergies tend to be to fruits and vegetables; it’s called pollen-food allergen syndrome.

Fish and shellfish are also common adult-onset allergies; again, these can be secondary sensitivities related to other foods. Allergies to fish nematodes can develop and then make you seem allergic to fish. (Nematodes are worms that are common in fish; no, I will not show you a picture because I cannot unsee it and will not subject you to it.)

You can develop an allergy to meat after a particular type of tick bite. Some adults develop an allergy to wheat that occurs only if they exercise within a couple of hours of eating wheat; this is called food-dependent, exercise-induced anaphylaxis. Adults can get allergies if they have an organ transplant, if the person from whom the organ is transplanted had the allergy; it isn’t a common cause.

I write all this partly because it’s just very interesting! But in addition, it illustrates that there is much we do not know in this area, and the data is thin. For typical childhood-onset allergies, we do not expect them to simply show up in adulthood or older childhood. If your child doesn’t have an egg allergy as a baby, they aren’t likely to show up with one at the age of 12. They could develop an allergy as an adult, perhaps due to fish worms, but there isn’t much you can do about that.