Food Allergy vs Food Intolerance: What’s the Difference?

Many people say they have a “food allergy,” but not all reactions to food are true allergies. Understanding the difference between a food allergy and a food intolerance is important, because the risks, testing, and treatment are very different.

What Is a Food Allergy?

A food allergy involves the immune system, specifically IgE antibodies. When someone with a food allergy eats even a small amount of the trigger food, their immune system reacts quickly.

Common symptoms of food allergy may include:

• Hives or itchy rash
• Swelling of the lips, tongue, face, or throat
• Vomiting or diarrhea shortly after eating
• Coughing, wheezing, or trouble breathing
• Dizziness or fainting

⚠️ Severe reactions (anaphylaxis) can be life-threatening and require immediate treatment with epinephrine.

Common food allergens include:

• Peanut, tree nuts
• Milk, egg
• Wheat, soy
• Fish and shellfish

How Is a Food Allergy Diagnosed?

Food allergies are diagnosed based on:

• A detailed clinical history
• Skin prick testing and/or blood testing
• In some cases, a supervised oral food challenge

Testing is only helpful when results match symptoms - testing without symptoms often leads to false positives.

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What Is a Food Intolerance?

A food intolerance does not involve the immune system. It usually affects digestion and tends to be dose-dependent - small amounts may be tolerated, while larger amounts cause symptoms.

Common symptoms of food intolerance include:

• Bloating or gas
• Abdominal pain
• Diarrhea
• Nausea
• Headache or fatigue

Symptoms are uncomfortable but not life-threatening.

Examples include:

• Lactose intolerance
• Sensitivity to caffeine
• Reactions to food additives or preservatives

Should You Get Tested?

This is a very common question - and the answer depends on your symptoms.

✔ Testing may be appropriate if:

• Symptoms occur quickly after eating
• There are hives, swelling, breathing symptoms, or vomiting
• There is a history of severe reactions

✖ Testing is usually not helpful if:

• Symptoms are delayed or vague
• The main issue is bloating or digestive discomfort
• Multiple foods “feel” problematic without clear reactions

At our clinic, we focus on targeted testing to avoid unnecessary food avoidance and anxiety.

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When Should You See an Allergist?

You should consider seeing an allergist if:

• You’re unsure whether your reaction is an allergy or intolerance
• You’ve been avoiding foods without a clear diagnosis
• Your child has had a concerning reaction to food
• You’ve been prescribed an epinephrine auto-injector and need guidance

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The Bottom Line

Not all food reactions are allergies - but true food allergies can be serious. Getting the right diagnosis helps ensure:

• You’re avoiding foods only when necessary
• You’re properly protected if there is a real allergy
• You’re not missing other treatable causes of symptoms

If you’re unsure, an allergist can help clarify what’s going on and guide safe next steps.

Please note:

We require a referral from your family doctor to schedule a consultation. They can fax the referral to 416-850-9993 or use our referral form under our FAQ page.