Food Intolerance vs Food Allergy: What’s the Difference?
Food intolerances and food allergies are often confused, but they are very different conditions. Understanding the difference is important if you’re experiencing digestive symptoms such as bloating, gas, diarrhoea, or constipation and want to address the root cause.
What Is a Food Intolerance?
A food intolerance occurs when the body has difficulty digesting or processing a particular food. Unlike food allergies, food intolerances do not involve a dangerous immune response, but they can still cause uncomfortable and disruptive symptoms.
Common symptoms of food intolerance include:
Bloating
Excess gas
Abdominal discomfort
Diarrhoea or constipation
Nausea
Fatigue and brain fog
Symptoms are often delayed and dose-dependent, meaning small amounts of a food may be tolerated, while larger portions trigger symptoms.
What Is a Food Allergy?
A food allergy involves the immune system, typically through IgE antibodies. Allergic reactions usually occur quickly after eating the food and can be serious.
Symptoms of food allergy may include:
Skin reactions such as hives or rashes
Swelling of the lips, tongue, or throat
Wheezing or difficulty breathing
Vomiting
Anaphylaxis (in severe cases)
Food allergies should always be diagnosed and managed by a medical professional.
Food Intolerance vs Food Allergy: What’s the Difference?
| Food Intolerance | Food Allergy |
|---|---|
| Digestive-related | Immune-system reaction |
| Symptoms may be delayed | Symptoms often immediate |
| Usually dose-dependent | Tiny amounts can trigger a reaction |
| Not life-threatening | Can be severe or life-threatening |
What Causes Food Intolerances?
In many cases, food intolerances are a sign of poor gut function, rather than a true intolerance to the food itself.
1. Low Stomach Acid
Adequate stomach acid is essential for breaking down food, particularly protein. Low stomach acid can lead to poor digestion, bloating, reflux, and increased food sensitivities.
2. Lack of Digestive Enzymes
Digestive enzymes help break food into absorbable nutrients. When enzyme production is low, food can ferment in the gut, leading to gas, bloating, and loose stools.
3. Gut Dysbiosis
An imbalance of gut bacteria can increase fermentation and sensitivity to certain foods, particularly carbohydrates.
4. Increased Intestinal Permeability (“Leaky Gut”)
When the gut lining becomes compromised, larger food particles can pass through the intestinal wall, triggering symptoms and immune activation.
5. Gut Inflammation or Infection
Previous gut infections, antibiotic use, chronic stress, or inflammation can all impair digestion and food tolerance.
Should I Take a Food Intolerance Test?
Many people turn to food intolerance tests when experiencing digestive symptoms, but it’s important to understand what these tests actually measure.
IgG Food Intolerance Tests: What You Need to Know
Most at-home food intolerance tests measure IgG antibodies to foods. While widely marketed, these tests have significant limitations:
IgG antibodies often reflect recent food intake, not intolerance
IgG production is a normal immune response to eating food
A positive IgG result does not mean a food is causing symptoms
IgG food tests are not medically recognised as a diagnostic tool
It’s common for these tests to show long lists of “intolerant” foods, leading to unnecessary restriction. In reality, the symptoms are often driven by underlying gut issues, not the foods themselves.
Why Removing Foods Isn’t Always the Answer
If digestion and gut health are compromised, many foods can trigger symptoms. Once the gut is supported and underlying imbalances are addressed, people are often able to reintroduce foods and eat them symptom-free.
This is why I don’t recommend relying on self-testing kits purchased online.
A Better Approach: Comprehensive Stool Testing
If you’re experiencing ongoing bloating, gas, constipation, or diarrhoea, a comprehensive stool test can provide far more meaningful insight.
Stool testing can help identify:
Imbalances in gut bacteria
Digestive enzyme insufficiency
Gut inflammation
Markers of gut barrier function
Possible infections or overgrowths
This allows us to address the root cause of symptoms rather than managing them with long-term food avoidance.
The Bottom Line
Food intolerances are often a symptom of poor gut health, not a permanent intolerance to specific foods. With the right investigation and support, many people can restore gut function and enjoy a wider, more varied diet again.
If you’re struggling with digestive symptoms and want personalised support, working with a qualified nutritionist can help you get clear answers and a targeted plan.