Symptoms of Food Intolerance
The symptoms of food intolerance usually affect the digestive system and can appear several hours after eating the trigger food. Food intolerance is often confused with allergy, but the symptoms tend to be less severe and more chronic or fluctuating in nature.
Digestive Symptoms
Bloating and gas
Abdominal cramps or pain
Diarrhoea or loose stools
Constipation, in some cases
Nausea or discomfort after eating
These symptoms are common in lactose intolerance, fructose malabsorption, and reactions to food additives.
Non-Digestive Symptoms
Some people with food intolerance may also experience:
Headaches or migraines, particularly after consuming caffeine, chocolate, or MSG
Flushing or skin irritation
Fatigue or brain fog, often linked to chemical sensitivities
Mood changes, such as irritability or anxiety, especially in children
Unlike allergies, food intolerances rarely involve swelling, breathing problems, or anaphylaxis.
Timing and Severity
Symptoms usually appear within a few hours after eating but can take up to 24–48 hours
Reactions are often dose-dependent—small amounts may not cause symptoms, but larger amounts do
People may tolerate the food occasionally but react after repeated exposure or stress
Common Triggers
Dairy – milk, cream, ice cream
Wheat and gluten-containing grains – bread, pasta, pastries
Onions, garlic, and legumes – high in fermentable sugars (FODMAPs)
Wine and processed meats – due to sulphites and other preservatives
When to Seek Help
If you notice:
Ongoing digestive problems, particularly after eating certain foods
Inconsistent symptoms, making it hard to identify the cause
Unexplained fatigue or mood changes
Weight loss or nutritional deficiencies
…you should consult a GP or dietitian.
Symptoms of Food Intolerance
Recognising the symptoms of food intolerance helps individuals track their triggers, reduce discomfort, and improve quality of life through manageable dietary adjustments.
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