Decoding Food Reactions: Allergies, Intolerances, and Sensitivities Explained

Pittsburgh Dietitian Blog Posts
June 11, 2024

The terms food allergy, intolerance, and sensitivity often get used interchangeably, but they represent distinct reactions within the body to certain foods. Let's delve into each category to examine the differences.


An allergy is an immune system response to a specific food triggered by immunoglobulin E (IgE) antibodies. This reaction is rapid and can be severe, sometimes leading to life-threatening anaphylaxis. Immediate symptoms typically occur within minutes to hours after consuming the allergen and can include hives, itching, swelling (especially around the mouth and throat), gastrointestinal distress, respiratory issues like wheezing, and in severe cases, anaphylactic shock.


Food intolerance refers to the body's inability to properly digest or process certain foods. Unlike allergies, which involve the immune system, intolerances are generally related to enzyme deficiencies or sensitivities to food components. Symptoms of intolerance are usually delayed and can range from mild to uncomfortable. Common signs include bloating, gas, indigestion, nausea, and diarrhea. Lactose intolerance, for instance, occurs due to a deficiency of the enzyme lactase, which is needed to digest lactose found in dairy products.


Food sensitivity is a broad term encompassing various reactions to foods that are not mediated by IgE antibodies but can involve other immune mediators like immunoglobulin G (IgG). Unlike allergies and intolerances, sensitivities often have a delayed onset, making them harder to pinpoint. Symptoms can manifest hours or even days after consuming the trigger food and may include headaches, joint pain, skin issues, digestive disturbances, fatigue, and mood changes.

The Bottom Line

Differentiating between these reactions is crucial for proper diagnosis and management. Allergies require strict avoidance of the allergen and may necessitate carrying epinephrine (EpiPen) for emergency situations. Intolerances may improve with enzyme supplements or dietary modifications, such as eliminating the offending food. Sensitivities often require a process of elimination and reintroduction to identify triggers accurately.

Consulting with healthcare professionals, such as allergists, gastroenterologists, or registered dietitians, is essential for accurate diagnosis and personalized management plans. Keeping a food diary and noting symptoms can also aid in identifying patterns and potential triggers. While allergies, intolerances, and sensitivities all involve adverse reactions to foods, they differ in their mechanisms, timing of symptoms, and severity. Understanding these distinctions helps individuals to make informed choices about their dietary habits and overall well-being.

If you are looking to speak to a registered dietitian about a food allergy, intolerance, or sensitivity, reach out to us at !

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