Food Allergy, Food Sensitivity, & Food Intolerance
1. What is the difference between a food allergy and a food sensitivity?
Food allergy, food sensitivity, and food intolerance. While these terms may sound similar and are often used interchangeably in everyday conversations, it is important to clearly define them as each has a precise meaning that does not overlap with the other two.
Food sensitivity – this is the simplest one. In the field of Allergy, food sensitivity is merely an abnormal test result. This means that you’ve either had a positive food allergy skin test or a food-specific IgE lab test demonstrating an abnormal value. It is important to remember, however, that having actual clinical symptoms is not a requirement for using this term, it is purely a test result.
Food allergy - this is arguably the most serious of the three. A food allergy is an adverse reaction resulting from a specific and reproducible immune response after food consumption. It is essentially your immune system going into overdrive, potentially affecting multiple organ systems, in response to a food you’ve consumed – think of the commonly known peanut and shellfish allergies. Also, as in the case of these classic examples, food allergies, if left untreated, may rapidly progress into life-threatening reactions, typically through airway occlusion.
Food intolerance – this is where it gets tricky. If you were to drink a glass of milk and then shortly after developed an upset stomach, you may refer to this as a “food sensitivity.” However, this is a colloquial use of the term and would be more precisely defined as a food intolerance (think lactose intolerance). A food intolerance is a nonimmunological reaction to a food, typically resulting from an inability to digest or break down that food properly. As such, lactose intolerant individuals are unable to process (they are intolerant of) lactose containing foods (milk and cheese). A notable difference between food intolerance and a food allergy is that while food allergies may have potentially life-threatening systemic effects, food intolerances are limited to the gastrointestinal tract and typically result in chronic digestive problems that do not carry the same risk.
Having delineated what these terms mean, in order to avoid confusion, for the remainder of the article we will stick to only two terms as they are defined above: food allergy vs. food intolerance.
2. What are the difference in the symptoms between a food allergy and food intolerance?
Food allergy reactions can have varied clinical presentations due to their effect on multiple different organ systems. The majority of food allergy reactions have skin manifestations, such as rash, itching, swelling and/or flushing. Aside from skin involvement, food allergies can also manifest with one or more of the following symptoms: nasal congestion, sneezing, red, watery eyes, throat itching/swelling/closure, shortness of breath, wheezing, stridor, cough, hoarseness, nausea, vomiting, diarrhea, reduced blood pressure, lightheadedness, loss of consciousness, incontinence of urine or stool and/or uterine contractions. On the other hand, the symptoms of food intolerance mainly effect the digestive system: crampy abdominal pain, flatulence, bloating, abdominal distension, diarrhea and/or constipation.
3. How is a food allergy diagnosed compared to a food intolerance?
The diagnosis of a food allergy includes a convincing history, skin prick testing, lab tests for food-specific immunoglobulin E (IgE) antibodies, and, if warranted, an oral food challenge. Your allergy physician may also use component-resolved diagnostics (CRD), which measures IgE antibodies to specific proteins within a food, such as storage seed protein Ara H2 in peanut, to better characterize the clinical significance of your food allergy. It is very important to work with an allergist in the interpretation of diagnostic testing for food allergy, as misinterpreted results often lead to unnecessary and difficult dietary restrictions and nutritional deficiencies.
There are tests the National Institute of Allergy and Infectious Diseases (NIAID) as well as the American Academy of Allergy, Asthma & Immunology (AAAAI) believe are not validated and not useful in the diagnosis of food allergy. These tests include food-specific IgG or IgG4 testing (a large-scale screening test looking for IgG or IgG4 antibodies to hundreds of different foods), applied kinesiology (testing muscle strength/weakness to diagnose food allergy), cytotoxicity testing, also known as Alcat tests (mixing white blood cells with a suspected food allergen and observing for cell shape change), electrodermal testing (applying electrical current to a patient while they hold a suspected food), hair analysis (examination of mineral content of hair to diagnose food allergy). Out of all these tests, possibly the best-known, marketed but unvalidated test for food allergies as well as intolerances is food-specific IgG or IgG4 testing. However, according to the European Academy of Allergy and Clinical Immunology (EAACI) and the AAAAI, IgG and IgG4 antibodies demonstrate previous exposure to food rather than food allergy or food intolerance.
In contrast, food intolerances more readily lend themselves to basic diagnostic approaches. According to the American Gastroenterological Association, the simplest, most cost-effective method to diagnose any food intolerance is dietary restriction of short duration (2 weeks) with observation for symptom improvement. Other testing modalities are available such as breath testing which measures hydrogen, methane and carbon dioxide to diagnose suspected sugar intolerances such as lactose, fructose or sucrose intolerances. Depending on the severity of your symptoms, your provider may recommend laboratory testing, imaging studies or invasive diagnostic testing measures such as endoscopy with biopsies.
4. Can someone outgrow their food allergies or intolerances?
The majority of children with food allergies to cow’s milk, soy, egg, and wheat outgrow their food allergies by their teenage years, whereas tree nut and seafood allergies are typically lifelong. Your allergist can perform annual testing to ascertain when your child has most likely outgrown their food allergy and the safest method of reintroduction, i.e.: oral challenge in the clinic setting vs. home introduction. In contrast, based upon currently available studies, it is unclear if patients outgrow their food intolerances.
5. When should someone discuss with their physician their food related symptoms?
It is difficult to provide a one size fits all type of checklist for when an individual should seek medical advice. Much of medicine, and the field of Allergy in particular, is personalized and nuanced. That being said, it is important to establish care with an allergist if you are having adverse food reactions or are avoiding foods due to concern for food allergy. Based upon your history, your allergist can use appropriate and validated testing to help diagnose and, if necessary, devise the most comprehensive diet that is safe for you.
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