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Two people can feel unwell after the same food for very different reasons. Food allergy and food intolerance can both affect everyday meals, but the distinction matters: their causes, risks and management are different.
Start with what is causing the reaction
A food allergy involves the immune system responding to a food, usually a protein. Reactions may include hives, swelling, vomiting or breathing difficulties. A severe allergic reaction, known as anaphylaxis, can be life-threatening. Some allergies cause delayed symptoms, so timing alone cannot identify the cause.
A food intolerance does not involve the same allergic immune response. It may relate to difficulty digesting or absorbing a food component. Lactose intolerance is a familiar example: insufficient lactase can leave some milk sugar undigested. Symptoms can include bloating, wind, abdominal discomfort and diarrhoea.
The Mayo Clinic overview of food allergy and Cleveland Clinic explanation of food intolerance provide further background.
Milk illustrates why the words matter
Milk contains both proteins and a sugar called lactose. A person with cow’s milk allergy reacts to milk protein. Someone with lactose intolerance has difficulty digesting lactose. Removing or breaking down lactose does not remove the milk proteins.
This means lactose-free dairy and lactase supplements are not ways to make milk safe for someone with cow’s milk allergy. ASCIA’s cow’s milk allergy information explains this distinction and the need for suitable dietary advice.
Symptoms and portions offer clues, not a diagnosis
With an intolerance, the amount of a food eaten can influence whether symptoms occur. Some people tolerate a small portion but experience discomfort with a larger one. Tolerance can also depend on the rest of the meal and the individual’s circumstances.
Food allergy requires a different approach. Small amounts of an allergen can cause a reaction, and a previous mild reaction does not establish that future exposure is safe. Do not experiment with suspected allergens to find a personal “safe amount”.
Stomach symptoms alone cannot reliably distinguish allergy from intolerance or from other digestive conditions. A clinician will consider the history, the timing and pattern of symptoms and whether appropriate testing is needed.
Where does “food sensitivity” fit?
People often use “sensitivity” to describe symptoms they associate with food. It is a broad expression, not a precise diagnosis or a single mechanism. Ask what a practitioner means by the term and what evidence supports the proposed explanation. Harvard Health discusses how these terms are used.
Prepare useful information for your appointment
- Record the food, ingredients and approximate amount eaten.
- Note when symptoms began, what they were and how long they lasted.
- Include any previous reactions and medicines or supplements used.
- Take photographs of relevant product labels if a meal had several ingredients.
Do not delay urgent care to complete a diary. If a reaction involves difficulty breathing, throat or tongue swelling, or collapse, follow any prescribed anaphylaxis action plan and call 000 in Australia.
Match management to the confirmed problem
An allergy management plan may involve avoiding the allergen, understanding food labels and having prescribed emergency medication available. Intolerance management may involve adjusting portions, identifying tolerated alternatives or considering a product intended for a specific food component.
Digestive enzymes are not diagnostic tests. An improvement after taking a supplement does not prove which condition is present, and enzymes do not treat food allergy. Our combination product collection and Australian product information explain the products available; choose with appropriate advice once the problem is understood.
For historical background, the original article linked to Cornell’s 2005 discussion of lactase persistence. Its population figures should not be treated as current Australian prevalence estimates.