Food allergies, intolerances and sensitivities are a hot button topic lately. The definitions are commonly confused so I thought I would take minute to clear it up.
Food Allergies: Food allergies are an immune reaction that result when our immune system attacks a harmless food protein (an allergen). The body produces a large amount of the antibody IgE (Immunoglobulin E) and releases chemicals (ex. histamine) which trigger symptoms of an allergic reaction.
Common food allergens: peanut, tree nut, milk, egg, wheat, soy, fish, shellfish, sesame
Symptoms: hives, rash, sneezing, stomach pain, redness of skin around eyes, nausea/vomiting, anaphylaxis (in extreme cases)
Diagnosing food allergies: There are several ways to test for food allergies.
Skin Prick Test – This is when the allergist drops solutions of food on your arm or back and waits about 30 minutes for a response. They are looking for a wheal and flare response which is a raised white bump surrounded by itchy red skin. The skin prick test has a 50-60% chances of showing a false positive meaning that you are not really allergic to the foods being tested. NOT IDEAL.
Blood Test – The blood tests do not help you predict the severity of an allergy but will tell you if you could have an allergy. It takes several days to get the results back, unlike the skin prick test. This tests can detect either your response to the undigested food proteins OR detect proteins that are similar among foods but do not trigger allergic reaction. Because of this the blood test also has a 50-60% chance of yielding a false positive result. NOT IDEAL.
Oral Food Challenge – This test is highly accurate but also has the potential to cause serious reactions and should only be done in the presence of an experienced allergist in a medical facility. During the food challenge, the allergist will feed you suspect foods in small doses repeatedly to see if there are any signs of a reaction. IDEAL.
Food Elimination Diet – A food elimination diet can be used to help diagnose a food allergy. During a 2-4 week period you eliminate any suspect foods while the doctor monitors symptoms. There is a gradual period of reintroduction when you add in suspecting foods and continue to monitor symptoms. IDEAL.
Food Intolerances: Food intolerances do not involve the immune system. Some food intolerances are caused by a lack of a particular enzyme. Symptoms may appear similar to a food allergy but they will never trigger anaphylaxis. Most of the time, symptoms of a food intolerance take longer to manifest than symptoms of food allergies.
Common food intolerances: lactose intolerance, celiac disease
Symptoms: bloating, stomach ache, hives, headaches/migraines, irritable bowel
Diagnosing food intolerances: There is no accurate, reliable and validated test to identify food intolerances. The best tool is an elimination diet. Foods and symptoms are monitored and analyzed for patterns between food intake and symptom manifestation.
Food Sensitivities: Food sensitivities, like food allergies, involve the immune system however they are not measuring IgE antibodies. Food sensitivities can occur with any food/chemical and reactions can occur up to 72 hours after ingesting the offending food. Sensitivities involve non-IgE antibodies and chemical mediators – because of this allergy testing will NOT test for them.
Common food sensitivities: ANY food or chemical
Symptoms: headaches/migraines, irritable bowel, bloating, diarrhea, joint pain, fatigue, etc. The list goes on and on.
Diagnosing food sensitivities:
ELISA/ACT Test – Uses an accurate measure of IgG however, adverse food reactions often involve more than just IgG reactions. For example, this test is not useful for IBS and migraines and it cannot test chemical reactions. IgG may appear high because it is acting as a protective antibody, in which case it may be a good thing. There are no published studies of reliability or validity.
ALCAT Test – Measures changes in white blood cell size after exposure to an antigen (food). While early studies showed good accuracy (86%) this is now an outdated technology and cannot measure lymphocyte reactions.
MRT Test – Measures changes in ratio of liquid to solids after whole blood exposure to an antigen (food). This test has excellent accuracy (94.5% sensitivity and 91.7% specificity) and reliability ( >90% split sample reproducibility). With this test we can measure food and chemical reactions by measuring the outcome of all sensitivity reactions. This is the best test for food sensitivities available at this time.
Susan Linke, food sensitivity expert and LEAP mentor does a great job explaining food sensitivities in this video.