There is a lot of confusion when it comes to the differences between food allergies and food sensitivities. Food allergies are primarily IgE antibody mediated and the immune reaction is almost immediate with symptoms including asthma, hives, lightheadedness, rhinitis, weakness, and life-threatening anaphylaxis. The most common IgE food allergies are cow’s milk, eggs, tree nuts, peanuts, shellfish, wheat, soy, and fish. Food protein-induced enteropathies are non-IgE mediated food allergies that involves the gastrointestinal tract and includes celiac disease, food protein-induced enterocolitis syndrome (FPIES), and proctitis/proctocolitis. Symptoms of food protein-induced enteropathies may include anemias, blood in stool, chronic diarrhea, delayed growth in infants and children, and vomiting. Other than gluten in celiac disease, soy and dairy proteins such as A1 β-casein are common triggers for food protein-induced enteropathies, but any food protein may cause symptoms.
Some environmental allergies such as latex allergy and pollen allergies can also cause food cross-reactivity allergy reactions due to similarities to proteins in the foods to proteins in the allergens. Latex fruit syndrome and pollen food allergy syndrome most often causes oral allergy symptoms including swelling, burning, itching, or hives in or around the mouth, lips, tongue, and throat within 2 hours of consuming a food. Foods that may cause a cross-reactivity reaction in those allergic to latex include apples, avocados, bananas/plantains, bell peppers, carrots, celery, chestnuts, eggplant, figs, kiwi, mango, melons, papaya, passionfruit, peaches, pears, pineapple, potatoes, soy, strawberries, and tomatoes; some of these foods contain natural latex, but not all of them. Birch pollen allergies may cause cross-reactivity to almonds, apples, apricots, carrots, celery, cherries, hazelnuts, kiwi, peaches, peanuts, pears, parsley, plums, and soy. Those with grass allergies may experience cross-reactivity to oranges, peaches, tomatoes, watermelon, and white potatoes. Ragweed allergies may be cross-reactive to bananas, cucumber, melons, white potatoes, and zucchini. There are many more pollen-food cross-reactivities so if you have seasonal allergies and experience oral allergy symptoms, speak to your allergist or healthcare provider about possible cross-reactive foods.
Food sensitivities, also called non-IgE mediated food sensitivity or non-allergic food sensitivity, are not IgE antibody mediated but may still involve an immune response with the formation of large antibody-antigen complexes (IgG antibodies) that can cause inflammatory symptoms due to intestinal barrier permeability. These IgG antibodies also form in response to frequently eaten foods and after the resolution of IgE mediated food allergies. IgG antibody testing is not specific enough to diagnosis food sensitivities, though the presence of multiple IgG antibodies can be used to diagnosis intestinal barrier permeability. Other causes of food sensitivities include imbalances of microbial flora in the gut, also known as gut dysbiosis, and reactions to other substances in foods such as fungi, FODMAPS, or ATIs, as discussed in my post on non-celiac gluten sensitivity. Symptoms of food sensitivities can arise up to 72 hours after ingestion of a food and include acne, fatigue, headaches, hives, inflammation, migraines, muscle aches and pain, rashes, as well as gastrointestinal symptoms.
Beside food allergies and sensitivities, food intolerances caused by genetic variances in enzyme pathways required to breakdown foods can also cause adverse reactions. The most common food intolerance is lactose intolerance with up to 75% of the world’s population not having the genes for lactase persistence after childhood. There are others, though, including inborn errors of fructose metabolism. Polymorphisms on both copies of the genes encoded for the production of the enzymes fructokinase, aldolase B, or fructose-1,6-bisphosphatase (FBPase) causes deficiencies of the enzymes needed for the breakdown of fructose. Inborn errors of fructose metabolism may cause gastrointestinal symptoms and liver damage; in infants it can cause failure to thrive. Having only one copy of the gene for fructose intolerance isn’t thought to make much of a difference in people’s health, but in my experience that isn’t true. People with only one copy of the gene for hereditary fructose intolerance (HFI) can experience nausea, abdominal pain, and dry coughs from ingesting too much sucrose or fructose.
Treatment and testing for food allergies, sensitivities, and intolerances vary. IgE-mediated food allergies can sometimes be successfully treated with immunotherapy, but permanent food avoidance is most often recommended. Children with common IgE mediated food allergies often outgrow them between the ages of 6-10, while those with FPIES and dairy protein-induced enteropathies often outgrow them between ages 2-4. Food sensitivities can often be treated with short term avoidance of the food (3-6 months) along with healing the intestinal barrier, improving digestion, and improving gut microbial flora balance. Treatment for food intolerances depends greatly on what enzymes are missing; those with lactose intolerance can take lactase to improve digestion of the food, but those with inborn errors of fructose metabolism have to avoid foods high in fructose and sucrose. Testing for food allergies involves IgE antibody testing as well as a standard elimination diet with controlled re-introduction of foods under the direct supervision of a health care provider since life-threatening anaphylaxis is possible with IgE-mediated allergies. IgG4 antibody testing is available for diagnosing intestinal barrier permeability as discussed above, but elimination diets with controlled re-introduction of foods are the gold standard for identifying possible food sensitivities. Since food sensitivities are not immediately life threatening, the food challenges can be done at home with the guidance of a nutritionist or other knowledgeable practitioner. Breath tests and genetic tests are available for those with food intolerances, depending on what type is suspected.