Can an adult develop a food allergy?

We do not know why it happens, but sometimes an adult becomes allergic to a food they have eaten before.  Usually the foods are not routinely eaten and are known to be strong allergens: nuts, fish and shellfish.  However, this type of allergy starting in adulthood is not very common.

The type of allergy that is common in adults, some estimating up to 10% having it, is allergy to raw fruits and vegetables.  This is actually related to pollen allergy.  We call this "oral allergy syndrome" or "Pollen-food syndrome".

When a person becomes allergic to certain pollens, they may end up with symptoms of itchy mouth/lips when eating raw foods that contain proteins that look like the pollen proteins as far as the immune system is concerned.  An example is that birch tree pollen protein is similar to “rock fruit” proteins like apple, peach, cherry and others. Ragweed is similar to melons.  The symptoms are usually not severe, but talk to your doctor.  Heating the food should make the symptoms go away because this makes the problem proteins fall apart. The symptoms vary a lot.  Some people with a pollen allergy have no problems, others respond to one or more of the related foods.  Symptoms can also vary seasonally, being worst during and just after the pollen season.