What Is the Difference Between Allergy and Intolerance?
- Fysiobasen
- Oct 8
- 3 min read
The terms allergy and intolerance are often used interchangeably, but they describe two very different physiological reactions in the body. Understanding the difference is important, as the treatment and management of these conditions are not the same. This article explains what happens in the body during allergy and intolerance, and how these reactions affect health.
What Is an Allergy?
An allergy is an overreaction of the immune system to substances normally considered harmless. When a person with an allergy comes into contact with an allergen, the immune system mistakenly identifies the substance as a threat and launches an attack.
Typical symptoms may include:
Itching
Rash
Swelling
Breathing difficulties
Anaphylaxis (in severe cases)
Common allergens include pollen, dust, pet dander, foods such as peanuts or milk, and certain medications. Allergic reactions can occur immediately or within a few hours after exposure.
How Does the Immune Response Work in Allergy?
When exposed to an allergen, the immune system of an allergic person produces antibodies called immunoglobulin E (IgE). These attach to mast cells and basophils. When the allergen binds to IgE, these cells release substances such as histamine, which is responsible for typical allergy symptoms including itching, swelling, and runny nose.
What Is Intolerance?
Intolerance, on the other hand, is not an immune reaction. Instead, it occurs when the body struggles to digest or process certain foods or substances, leading to digestive problems.
Symptoms of intolerance may include:
Bloating
Stomach cramps
Gas
Diarrhea
The most well-known example is lactose intolerance, in which the body cannot break down lactose (the sugar in milk) due to insufficient levels of the enzyme lactase.
How Does Intolerance Work in the Body?
With intolerance, the body lacks the necessary enzyme or mechanism to handle specific foods. In lactose intolerance, for example, undigested lactose passes into the large intestine, where bacteria break it down, producing gas and causing bloating and diarrhea.
Key Differences Between Allergy and Intolerance
Immune response: Allergy involves an abnormal immune reaction, while intolerance relates to digestion problems without immune involvement.
Symptoms: Allergies can be severe and life-threatening (e.g., anaphylaxis). Intolerance typically causes digestive discomfort such as bloating or diarrhea.
Treatment: Allergies are often treated with antihistamines, allergy shots, or strict avoidance of allergens. Intolerance is managed by reducing or avoiding the problematic food, or by using enzyme supplements (e.g., lactase).
Timing: Allergic reactions often occur rapidly after exposure, while intolerance
symptoms develop more gradually.
How Are Allergy and Intolerance Diagnosed?
Allergy: Blood tests or skin prick tests are commonly used to identify specific allergens.
Intolerance: Diagnosis often involves elimination diets or tests such as a lactose tolerance test or fructose malabsorption test.
Are Allergy and Intolerance Dangerous?
Allergies can be life-threatening, particularly in cases of anaphylaxis, and require immediate medical attention. Intolerance, however, is rarely life-threatening. While it can cause significant discomfort and affect quality of life, it typically does not result in severe complications unless untreated over a long period.
Summary
Both allergy and intolerance can cause unpleasant symptoms, but they result from different mechanisms in the body. Allergy involves an abnormal immune response and can be severe, while intolerance is linked to the body’s inability to digest certain substances. Understanding the difference can help in better management and proper treatment of these conditions.
Sources
Galli SJ, et al. The cellular and molecular mechanisms of allergic diseases. Journal of Allergy and Clinical Immunology, 2003.
Ghosh S, et al. Lactose intolerance: A review of current concepts. Indian Journal of Gastroenterology, 2019.
Sicherer SH, et al. Food allergies: An overview. Pediatric Clinics of North America, 2003.
Lacy BE, et al. Rome IV criteria for functional gastrointestinal disorders. Gastroenterology, 2016.
American College of Allergy, Asthma, and Immunology (ACAAI). Understanding food allergies. ACAAI Website, 2020.
