⚠️ Medical Disclaimer
This guide is for food intolerances (non-life-threatening reactions), not food allergies (which can cause anaphylaxis). If you suspect a food allergy (hives, swelling, difficulty breathing), consult an NHS GP or allergist immediately. Never self-diagnose severe allergies.
What Is a Food Intolerance?
A food intolerance is a digestive or systemic reaction to a food that doesn't involve the immune system (unlike allergies). Common symptoms appear 30 minutes to 48 hours after eating trigger foods:
- Bloating, gas, stomach cramps
- Diarrhoea or constipation
- Headaches or migraines
- Skin issues (eczema, acne, rashes)
- Fatigue or brain fog
- Joint pain
- Nausea
Most common food intolerances in the UK: Lactose (dairy), gluten/wheat, FODMAPs, histamine, sulfites, food additives (E-numbers), caffeine.
Step-by-Step: How to Track Food Intolerances
Step 1: Start a Detailed Food Diary (2 Weeks)
Before changing your diet, track everything you eat and any symptoms for 2 weeks to establish patterns.
What to log daily:
- Time: When you ate (e.g., "8:00 AM")
- Food & drink: Exact items, including sauces, seasonings, cooking oils
- Portion size: Reactions can be dose-dependent
- Symptoms: Type, severity (1-10), time of onset
- Other factors: Stress, sleep quality, exercise, menstrual cycle (affects symptoms)
Example entry:
8:00 AM: Bowl of cornflakes (150g) with semi-skimmed milk (200ml), black coffee
10:30 AM: Bloating (6/10), stomach cramps (4/10), gas
Notes: Slept poorly last night (5 hours), stressed about work
Step 2: Analyze Patterns
After 2 weeks, review your diary for patterns:
- Do symptoms always appear after dairy? → Possible lactose intolerance
- Do headaches follow bread, pasta, or cereal? → Possible gluten sensitivity
- Do you feel worse after onions, garlic, beans? → Possible FODMAP intolerance
- Is bloating worse during your period? → Hormones amplify food reactions
💡 Use a Food Tracking App
NutraSafe lets you log meals with timestamps and add symptom notes for each entry. The app highlights patterns by showing which foods you ate before symptoms appeared, making it easier to spot triggers than paper diaries.
Step 3: Choose a Suspect Food to Eliminate
Based on your diary patterns, pick one food group to eliminate completely for 3-4 weeks. Removing multiple foods simultaneously makes it impossible to identify specific triggers.
Common elimination targets:
- Dairy (lactose): Milk, cheese, yogurt, butter, cream, whey protein
- Gluten: Wheat, barley, rye (bread, pasta, cereal, baked goods)
- High-FODMAP foods: Onions, garlic, beans, apples, wheat (complex—use Monash app)
- Eggs: Whole eggs, mayonnaise, baked goods
- Soy: Tofu, soy milk, soy sauce, edamame
Step 4: Eliminate Completely for 3-4 Weeks
100% elimination is critical. Even small amounts can trigger symptoms and invalidate your test. Read ingredient labels obsessively.
Hidden sources to watch for:
- Dairy: Whey, casein, lactose in processed foods, medications
- Gluten: Soy sauce, stock cubes, beer, processed meats
- Eggs: Pasta, baked goods, mayonnaise, meatballs
Track symptoms weekly: Most people notice improvement within 7-14 days if the food was truly the trigger. By week 3-4, symptoms should be significantly reduced or gone.
Step 5: Reintroduce the Food (Challenge Test)
After 3-4 symptom-free weeks, reintroduce the eliminated food deliberately to confirm it's the trigger.
How to reintroduce safely:
- Choose a test day: Pick a day when you're rested, not stressed, and can monitor symptoms
- Eat a normal portion: Have the food at breakfast (e.g., glass of milk, slice of bread)
- Wait 2-3 days: Monitor for symptoms (some reactions are delayed)
- Document everything: Log symptoms, severity, timing
Interpreting results:
- Symptoms return: You've confirmed the intolerance. Avoid this food or limit portions.
- No symptoms: It might not be the trigger. Reintroduce fully and test another suspect food.
- Mild symptoms: You may tolerate small amounts. Test different portion sizes.
Common Food Intolerances and Symptoms
| Food Intolerance | Primary Symptoms | Onset Time |
|---|---|---|
| Lactose (Dairy) | Bloating, gas, diarrhoea, stomach cramps | 30 mins - 2 hours |
| Gluten/Wheat | Bloating, fatigue, brain fog, diarrhoea, headaches | 2-48 hours |
| FODMAPs | Severe bloating, gas, IBS-like symptoms | 2-6 hours |
| Histamine | Headaches, flushing, hives, nasal congestion | 30 mins - 2 hours |
| Sulfites | Headaches, breathing issues, skin reactions | 15-30 mins |
| Food Additives | Hyperactivity (children), headaches, skin issues | 1-24 hours |
Best Apps for Tracking Food Intolerances
1. NutraSafe
Best for UK users. Designed specifically for tracking food reactions with barcode scanning and symptom logging.
- ✓ Log meals with timestamps
- ✓ Add symptom notes to each entry
- ✓ Pattern recognition highlights suspect foods
- ✓ Scan barcodes to check for allergens/additives
- ✓ Export data for doctor appointments
2. Cara Care (IBS Focus)
Best for FODMAP tracking. Specializes in IBS and digestive issues.
- ✓ Symptom tracking with severity scales
- ✓ FODMAP content database
- ✗ Requires subscription for full features
3. MySymptoms Food Diary
Best for detailed analysis. Generates reports showing food-symptom correlations.
- ✓ Comprehensive symptom tracking
- ✓ Statistical analysis of triggers
- ✗ Cluttered interface
Tips for Successful Food Intolerance Tracking
- Be patient: It takes 3-6 weeks per food to test properly. No shortcuts.
- Track everything: Even "healthy" foods can be triggers (almonds, spinach, etc.)
- Test one food at a time: Eliminating 5 foods at once = confusion
- Check for hidden ingredients: Lactose in bread, gluten in soy sauce, etc.
- Consider portion size: You might tolerate 50ml milk but not 250ml
- Account for stress: Stress amplifies food reactions—note stressful days
- Work with a dietitian: NHS referrals available for complex cases
When to See a Doctor
Consult your NHS GP if you experience:
- Unintentional weight loss
- Blood in stool
- Severe abdominal pain
- Symptoms lasting months despite elimination
- Suspected coeliac disease (requires blood test + endoscopy)
- Need to eliminate multiple food groups (malnutrition risk)
Track Food Intolerances with NutraSafe
Log meals, track symptoms, and discover your trigger foods. Barcode scanning checks for allergens instantly. Pattern recognition shows what you ate before reactions. Export data for doctors.
Download NutraSafe (Free)