My patients often come to me with allergy symptoms they associate with the season, but often we find that they are exacerbated by the foods they're eating.
Hives, digestive discomfort, post-nasal drip---these can all raise concerns about possible food allergies or intolerances. While people may use the terms interchangeably, it's vital to distinguish the two to deal with any symptoms you may see from your diet.
Food allergies: immune system activation
A food allergy occurs when the body identifies a particular food as harmful, triggering an adverse immune reaction.
This response is most often mediated by Immunoglobulin E IgE antibodies (E for emergency) which attach to immune cells such as mast cells and basophils, concentrated in areas like the skin, respiratory system, and gastrointestinal tract.
When the body encounters the allergen again, these IgE-primed cells release inflammatory chemicals such as histamine, which contributes to the symptoms of an allergic reaction such as hives, itching, and swelling.
Reactions can vary widely; in some cases, they may be mild and manageable with antihistamines, while in others, symptoms can escalate if untreated. In severe cases, anaphylaxis can occur.
The 9 food allergens in North America are: fish, shellfish, milk, eggs, soy, wheat, tree nuts, sesame and peanuts.
Food intolerances: digestive or enzyme-related issues
Food intolerances, unlike allergies, don't involve the immune system. Instead, they usually stem from the body's inability to properly break down certain foods due to enzyme deficiencies or digestive issues.
Symptoms of food intolerances are generally milder than allergic reactions and primarily manifest as digestive discomfort (e.g., bloating, gas, diarrhea, abdominal pain, nausea), although they can also include headaches, congestion, fatigue, and skin issues.
One common example of an intolerance is lactose malabsorption. Gut bacteria ferment this undigested lactose in the small intestine, producing gas, bloating, and diarrhea.
Histamine intolerance is another example, where the body can't properly break down histamine due to reduced activity of the enzyme diamine oxidase (DAO). Histamine is found naturally in foods like aged cheeses, cured meats, and fermented vegetables. Certain foods, such as tomatoes, chocolate, avocados, spinach, and eggplant, also trigger the body to release histamine. For histamine-intolerant people, eating too many of these foods may lead to symptoms both within and beyond the digestive system, including headaches, skin rashes, and congestion.
Key differences between food allergies and intolerances
Although some characteristics of food allergies and intolerances may overlap, there are essential differences in the mechanisms behind these reactions and how they affect the body. Understanding these distinctions is important for diagnosis and treatment.
Immune system vs. digestive issues -
Food allergies involve the immune system's response to specific proteins in food, whereas intolerances are caused by digestive issues, enzyme deficiencies, or chemical sensitivities.
Severity of reactions -
Allergic reactions can range from mild to life-threatening, with some allergies resulting in anaphylaxis, which can be fatal if not treated immediately. This potential for severe reactions means that food allergies require strictly avoiding the allergen and emergency preparedness, including access to an epinephrine auto-injector (EpiPen). Food intolerances, by contrast, typically lead to discomfort rather than danger.
Time of onset -
Allergic reactions usually occur within minutes to an hour after consuming the allergen. Intolerance symptoms, however, may take hours or even days to show up, which can make identifying trigger foods more challenging.
Diagnosis and medical evaluation -
Proper diagnosis is essential to distinguish between food allergies and intolerances, as management of each requires a different approach.
Diagnosing food allergies:
Doctors commonly use skin prick or blood tests to diagnose allergies, with skin prick tests generally considered the best approach.
In a skin prick test, a small amount of the suspected allergen is applied to the skin, which is then pricked to introduce it beneath the surface. If a reaction occurs, it suggests a potential allergy. Blood tests measure levels of IgE antibodies specific to particular allergens.
Diagnosing food intolerances
The gold standard diagnostic test for food intolerances is often an elimination diet, where you remove common trigger foods from your diet and reintroduce them one at a time. If done correctly, this test isolates the effect of each food on the body.
I commonly use a different finger prick test called The IgG Food Explorer (include image) which uses an ELISA-based microarray testing panel that specifically and sensitively quantifies IgG antibodies present within a sample.
This is a convenient collection that offers impactful insight into symptoms caused by foods so we can tie symptoms directly back to adverse reactions to foods. Food sensitivities can then be addressed through diet to help resolve symptoms and optimize health
Managing food allergies
People with food allergies must avoid their allergens altogether. For example, someone with a peanut allergy must restrict all forms of peanuts, such as peanut butter and peanut oil. They must also be careful about cross-contamination risks. Reading food labels, being vocal at restaurants, and educating family, friends, and colleagues about the allergy can all help keep them safe.
Managing food intolerances
People with food intolerances can sometimes tolerate small amounts of their trigger foods. They can also use supplements, such as lactase for lactose intolerance. Being mindful of portion sizes and selective with trigger foods is also helpful. For example, a histamine-intolerant person may be able to have a little bit of avocado on toast at breakfast but have more difficulty if they add an omelet with spinach and tomato.
Practical tips for managing food reactions in daily life:
Read labels thoroughly-
Allergens may be hidden or have alternative names. For example, wheat could be labeled as gluten or barley malt, and people with lactose intolerance should watch for lactose-containing foods like milk, cream, yogurt, and certain processed foods that use lactose as an ingredient.
Educate friends and family-
Inform people you frequently share meals with about your needs, such as avoiding certain ingredients or using separate utensils to provide cross-contamination. It will also likely increase support. Providing alternate recipe ideas or hosting a safe dinner are fun ways to make your restriction known and understood.
Carry safe snacks or alternatives-
Carrying safe alternatives to social gatherings and events can decrease stress and risk. Options that many people can tolerate include fresh fruit like apples or bananas, plain rice cakes, seed-based snack bars, gluten-free crackers, and individual packets of nut or seed butters. These snacks are transportable and keep well, making them easy to stash in your backpack or purse.
Communicate with restaurant staff-
Informing restaurant staff about dietary needs will significantly reduce the chances of an adverse reaction. Clearly explain any allergies or intolerances to the server and ask questions about food preparation, as cross-contamination can occur in kitchens. Calling ahead and speaking with the manager or chef can also be helpful.
Food allergies can cause severe, life-threatening reactions and require strict avoidance of the allergen. Intolerances, on the other hand, can be handled more flexibly with strategies like portion control and digestive support. Recognizing the critical distinctions between food allergies and intolerances allows people to make informed choices that keep them safe and symptom-free. With the proper knowledge, it's possible to enjoy food without worrying about unexpected reactions.