Food allergies are often confused with food intolerances. If you're unsure which is which, read on to find out how each differs and which tests can verify whether you suffer from an allergy or an intolerance.
Sometimes sitting for a peaceful meal can feel more like running an obstacle course if you have reactions to what you eat. But are you allergic, or is it something else?
What is a food allergy?
True food allergies trigger an immune system response. Immunoglobulin E (IgE)-mediated food allergies activate the adaptive immune system, which is typically on high alert to detect and fend off potentially dangerous parasites and pathogens.
In the case of an allergic reaction, instead of fighting off invaders, IgE binds to benign substances such as food proteins. These immune system triggers are known as allergens. In terms of food allergies, contact usually occurs through eating, but skin exposure or inhalation of food residue may also activate a response.
Allergen binding causes the release of inflammatory substances that promote recognizable allergy symptoms:
- Skin reactions (hives, rash, swelling) are the most frequent symptoms associated with IgE-mediated food allergies, and occur in 80 percent of allergic reactions.
- Gastrointestinal symptoms include nausea, vomiting, diarrhea, and abdominal pain.
- Respiratory problems may include itchy and runny nose, sneezing, spasms in vocal chords, and wheezing as well as itchy palate and swelling of lips or tongue.
- Low blood pressure may cause dizziness and/or fainting.
- In severe instances, anaphylactic reactions to an allergen cause a systemic response of inflammatory mediators that may have fatal consequences.
To be classified as an IgE-mediated response to a food, symptoms must occur within two hours of exposure.
Most common allergens
Between 4 and 7 percent of preschool-aged children experience IgE-mediated food allergies, and the number declines to 1 to 2 percent in adults. In children, 85 percent of food allergies involve
- cow milk
In adults, the most common allergens include
- tree nuts
The immune system processes underlying the three main non-IgE-mediated allergies that typically affect babies and young children (food protein-induced enterocolitis syndrome, food protein-induced proctocolitis, and the food protein-induced enteropathies) are not yet understood.
Common non-IgE-mediated allergens include the protein in cow milk and soy, but chicken, rice, and fish may also be problematic for some. Exposure to allergens typically causes a gastrointestinal response that may damage intestinal epithelial cells (cells that line intestinal surfaces). These allergies frequently end in childhood.
How do I test for a food allergy?
A thorough history helps to identify the cause of symptoms and to determine whether the reaction is IgE-mediated. This information also helps to guide appropriate testing. Unfortunately, allergy tests are sensitive but not specific. Due to the potential danger of allergy tests, they are typically performed in a specialized clinic.
Skin prick tests
Although not very accurate (except for anaphylactic reactions), these tests are usually the first step in allergy diagnosis. Food extracts and controls are applied to the skin, and then the area is pricked. After 20 minutes, any reaction is measured to determine clinical significance.
Blood antibody tests
Potential allergens are incubated with blood and then food-specific IgE antibody levels are measured. The various forms of this test are all reliable, but they use different reference points.
Double-blind placebo-controlled food challenge
This test involves the patient eating increasing amounts of a food or placebo while the practitioner monitors symptoms; the process is repeated a few days later, switching the solutions. Neither the patient nor the practitioner is aware of which substance is used during the test.
What is a food intolerance?
Rather than involving the immune system, food intolerances induce undesirable reactions to food through a variety of other mechanisms, described below.
Food intolerances may play a role in irritable bowel syndrome, which is a chronic gastrointestinal disorder. Adverse reactions to food may also include
- gastrointestinal symptoms
- respiratory symptoms
- itchy and runny nose
- watery eyes
Unlike allergic reactions, which are usually immediate, reactions due to non-allergic sensitivities can be delayed up to several days and are often long-lasting. Although a minute amount of an allergen will prompt an immune response, some people who experience food intolerances have a threshold for the offending food and can take it in small amounts; larger quantities or more frequent consumption of the food will bring about a reaction.
What causes a food intolerance?
There are many possible explanations for a food intolerance. Reactions could occur due to a deficiency in an enzyme required to break down the trigger food, which is what occurs in the case of lactose (milk sugar) intolerance. In the case of lactose intolerance, gastrointestinal responses are common and include bloating, cramps, diarrhea, and flatulence.
Fructose intolerance, on the other hand, involves the inability to absorb fructose (found in fruits and added to some foods as a sweetener), or it may be induced by an imbalance of fructose to glucose in the intestines. Unabsorbed fructose ferments in the colon and leads to symptoms that are similar to lactose intolerance.
Overconsumption of a food or food additive can cause unpleasant consequences in some people. In other instances of food intolerance, there is as yet no explanation.
Is gluten intolerance real?
Unlike celiac disease, which is an autoimmune disease triggered by eating gluten, non-celiac gluten sensitivity (NCGS) is a recognized condition associated with gluten consumption. In people who are affected, eating gluten may cause severe gastrointestinal symptoms, as well as systemic responses including anemia, brain fog, chronic fatigue, depression, joint and muscle pain, numbness in extremities, weight loss, and changes in attention. In order to diagnose NCGS, both celiac disease and wheat allergy must first be ruled out.
How is a food intolerance diagnosed?
Elimination diets may be the most effective—if most cumbersome—method of isolating a food culprit. Strictly avoid all suspect foods for at least two weeks to establish whether symptoms abate. Then, reintroduce one food at a time, spaced out over a few days, to determine if symptoms reappear.
Can I do an elimination diet on my own?
Because avoiding food groups may restrict your nutrient intake, it’s best to work with a nutritionist or naturopath to ensure you don’t become deficient. a
Naturally occurring chemicals and food additives are linked with food intolerances, including
- Amines: beer, cheese, chocolate, wine, yeast extracts
- Glutamates: cheese, tomato, mushrooms, stock cubes, and yeast extracts
- Salicylates: beer, nuts, spices, tea and coffee, wine, herbs and spices, jam, honey, and yeast extracts
- Additives: flavour enhancers (monosodium glutamate), artificial sweeteners, colourings, preservatives, and sulphites
Did you know?
Worldwide, most people are not able to absorb lactose, but the majority don’t experience symptoms.
Be proactive, not reactive!
Since many sensitizing reactions begin in the gut, it may be helpful to support your gastrointestinal tract. Beneficial bacteria known as probiotics help to promote digestion, regulate the immune system, and reduce allergic responses.
These help to assimilate nutrients. The enzyme lactase, for example, helps with absorption of lactose.
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) from fish oil help to modulate the immune system and are potentially allergy protective.