Food Sensitivities and Elimination Diets
The difference between allergy, intolerance, and sensitivity, and how to use an elimination diet to find triggers.
TL;DR
- 01A food allergy is an immune-mediated reaction (IgE) that can be life-threatening; a food intolerance is non-immune and dose-dependent; a food sensitivity is an umbrella term for chronic reactions that don't fit neatly into either category.
- 02The gold standard for identifying food sensitivities is an elimination diet followed by a structured, blinded reintroduction — not IgG blood panels, which have no clinical validity for food sensitivity.
- 03Elimination diets should be run under dietitian supervision to prevent nutritional deficiencies, especially in children or during pregnancy.
Tips
- 01Celiac disease is an autoimmune condition, not a sensitivity — it requires strict, lifelong gluten avoidance and must be diagnosed with blood tests (anti-tTG IgA) and intestinal biopsy before starting a gluten-free diet.
- 02A positive reaction in the reintroduction phase means that food is a trigger at that dose — not necessarily that it must be avoided forever. Many intolerances are dose-dependent, and ongoing testing over months can reveal how much you can tolerate without symptoms.
- 03Before starting an elimination diet, have your GP check for celiac disease antibodies (anti-tTG IgA), thyroid function, and complete blood count — many non-specific symptoms blamed on food have other, easily diagnosed causes.
Warnings
- 01If you suspect a true food allergy (especially to nuts, shellfish, or sesame), see an allergist before attempting elimination — an anaphylactic reaction during unsupervised reintroduction can be life-threatening.
- 02Elimination diets are nutritionally restrictive and can easily lead to deficiencies in calcium, vitamin D, B vitamins, and fiber if poorly planned. Do not extend the elimination phase beyond 6 weeks unnecessarily.
Allergy vs Intolerance vs Sensitivity
These three terms are frequently conflated in popular culture but have distinct mechanisms, severity profiles, and diagnostic approaches.
| Feature | Food Allergy | Food Intolerance | Food Sensitivity |
|---|---|---|---|
| Mechanism | IgE-mediated immune response | Enzymatic or chemical (non-immune) | Non-IgE immune or gut-mediated; poorly defined |
| Onset of symptoms | Minutes to 2 hours | 30 min – 48 hours | Hours to days |
| Dose dependency | Even trace amounts can trigger | Dose-dependent — small amounts often tolerated | Varies; often dose-dependent |
| Severity | Potentially life-threatening (anaphylaxis) | Uncomfortable but not dangerous | Chronic; debilitating but not acutely dangerous |
| Symptoms | Hives, throat swelling, anaphylaxis | Bloating, gas, diarrhea, headache | Fatigue, brain fog, skin, GI, joint symptoms |
| Diagnosis | Skin prick test, specific IgE blood test, oral food challenge | Symptom history, breath tests (lactose, fructose) | Elimination diet + reintroduction |
| Valid test | IgE testing (allergy specialist) | Lactose: hydrogen breath test; Histamine: clinical history | Elimination-reintroduction (gold standard) |
The popular IgG food sensitivity test sold by commercial labs lacks clinical validity — elevated IgG antibodies to foods indicate exposure, not pathology, and are found even in healthy individuals who regularly eat those foods. Major allergy societies (AAAAI, BSACI) do not recommend IgG testing for food sensitivity diagnosis.
Common Food Sensitivities
While any food can theoretically cause sensitivity in an individual, certain foods and food components account for the majority of reported reactions. Many sensitivities are actually to specific components within a food rather than the whole food.
| Trigger | Mechanism | Typical symptoms | Estimated prevalence |
|---|---|---|---|
| Lactose | Lactase enzyme deficiency → undigested lactose ferments in colon | Bloating, gas, diarrhea (30–120 min after dairy) | ~65% of adults globally; higher in East Asian, African, Hispanic populations |
| Gluten (non-celiac) | Not fully understood; may involve innate immunity or FODMAP fructans | GI symptoms, fatigue, brain fog (distinct from celiac disease) | ~1–6% of population (contested) |
| FODMAPs | Fermentable carbohydrates (fructose, lactose, fructans, galactans, polyols) ferment rapidly | Bloating, gas, pain, altered bowel habits — particularly in IBS | ~10–15% of population (IBS prevalence) |
| Histamine | Diamine oxidase (DAO) enzyme insufficiency; dietary histamine exceeds clearance capacity | Headache, flushing, hives, nasal congestion after aged foods | ~1–3% of population; poorly studied |
| Fructose (malabsorption) | GLUT5 transporter limitation → excess fructose in colon | Bloating, loose stools, pain especially after fruit, honey, HFCS | ~30–40% of adults have some degree |
| Salicylates | Aspirin-like compounds in many fruits, vegetables, and spices | GI symptoms, skin reactions, asthma-like symptoms in sensitive individuals | Rare; ~0.1–2% |
How an Elimination Diet Works
The elimination diet is a structured diagnostic tool, not a permanent way of eating. The goal is to remove potential trigger foods for 3–6 weeks until symptoms resolve, then systematically reintroduce them to identify which food (or food component) is causing the problem.
The most comprehensive version is the low-FODMAP diet (for IBS) or the broader six-food elimination diet used in eosinophilic esophagitis (removing milk, wheat, eggs, nuts, soy, and seafood). For general sensitivity investigation, a more practical two-stage process is standard:
- Stage 1 — Elimination (3–6 weeks): Remove all suspected trigger foods completely. Consume only whole, minimally processed foods from a base list. Keep a detailed symptom diary throughout.
- Stage 2 — Reintroduction: Reintroduce one food group at a time, every 3 days, while monitoring symptoms. If symptoms return, remove that food and wait for symptoms to clear before testing the next.
| Phase | Duration | Allowed foods | Goal |
|---|---|---|---|
| Elimination | 3–6 weeks | Rice, quinoa, most vegetables, chicken, turkey, lamb, non-citrus fruits, olive oil, coconut oil | Achieve symptom remission as baseline |
| Reintroduction | 6–12 weeks (testing each group) | One new food group every 3 days | Identify specific triggers |
| Personalized diet | Ongoing | All tolerated foods + avoiding confirmed triggers | Maximum dietary variety without symptoms |
Reintroduction Phase
The reintroduction phase is where the diagnostic value is gained — and where most people go wrong by reintroducing multiple foods simultaneously or not waiting long enough between tests. Patience and systematic testing are essential for reliable results.
- Test one food or food group at a time — combine a trigger food with a baseline meal, not with other new introductions.
- Use a structured dose escalation — a small portion on day 1, a medium portion on day 2, a full portion on day 3, then observe for 3 days before testing the next food.
- Document carefully — use a symptom diary scoring 0–10 for each symptom category (GI, skin, energy, cognition) at the same times each day.
- Wait for symptoms to clear before testing another food after a positive reaction — residual symptoms confound results.
| Reintroduction order (low-FODMAP example) | Foods tested | Wait before next group |
|---|---|---|
| Lactose | Milk, soft cheese, ice cream | 3 days if no reaction |
| Fructans (wheat) | Wheat bread, pasta (2 portions) | 3 days if no reaction |
| Fructose (excess) | Honey, mango, apple juice | 3 days if no reaction |
| Galacto-oligosaccharides | Chickpeas, lentils, cashews | 3 days if no reaction |
| Polyols (sorbitol) | Avocado, peaches, stone fruits | 3 days if no reaction |
| Polyols (mannitol) | Mushrooms, cauliflower | 3 days if no reaction |
Working with a Dietitian
Self-directed elimination diets carry real risks: nutritional deficiencies (especially in children), unnecessarily prolonged restriction, and incorrect attribution of symptoms to the wrong food. A registered dietitian (RD) or accredited practising dietitian (APD) significantly improves outcomes.
A dietitian provides:
- Nutritional adequacy review — ensures the elimination diet still meets calorie, protein, calcium, vitamin D, and fiber requirements.
- Symptom diary interpretation — identifies patterns that may not be immediately obvious to the individual.
- Guidance on specific protocols — the FODMAP approach, for example, is complex and requires professional training to implement correctly; Monash University's low-FODMAP app is dietitian-developed.
- Psychological support — food restriction can trigger anxiety around eating; a dietitian supports a healthy relationship with food throughout the process.
| Resource type | Use | Notes |
|---|---|---|
| Registered dietitian | Whole-protocol supervision | Essential for children, pregnant women, complex symptoms |
| Monash FODMAP app | Low-FODMAP food guide | Research-backed; updated regularly; small cost |
| GP / gastroenterologist | Rule out celiac, IBD, SIBO before starting elimination | Bloodwork and endoscopy may be needed first |
| Symptom diary apps | Consistent daily logging (e.g., mySymptoms, GI Monitor) | Improves pattern recognition; share with clinician |
FAQ
Most elimination diets run for 3–6 weeks, which is typically enough time for chronic symptoms to clear if a trigger food has been removed. Shorter periods risk missing slower-onset reactions, while unnecessarily long elimination phases increase the risk of nutritional deficiencies.
A food allergy involves an IgE-driven immune response that can cause rapid, systemic symptoms including anaphylaxis, even from trace amounts. A food intolerance — like lactose intolerance — is non-immune and dose-dependent, meaning small quantities are often tolerated without symptoms.
IgG antibodies reflect food exposure, not sensitivity — most people produce them against foods they eat regularly, regardless of whether those foods cause symptoms. Because elevated IgG is a normal immune response, a positive result is clinically meaningless for diagnosing food sensitivity and often leads to unnecessary food restriction.
Reintroduce one food at a time in a pure, isolated form and wait 2–3 days before testing the next food, so any returning symptom can be clearly linked to a specific trigger. Keeping a symptom journal during this phase makes it much easier to spot patterns that might otherwise be missed.
Elimination diets during pregnancy, breastfeeding, or childhood carry a high risk of nutritional gaps and should always involve a registered dietitian. Adults with a history of eating disorders or significant unintentional weight loss should also get clinical oversight before restricting entire food groups.