Powerful Features for Food Intolerance Management

A food intolerance is an adverse reaction to a food or food component that does not involve the immune system (unlike a food allergy). It typically occurs when your body lacks the enzymes needed to digest certain substances, or when specific food chemicals irritate your digestive system or nervous system. Symptoms are usually delayed (appearing 2–72 hours after eating), dose-dependent (small amounts may be tolerated), and primarily affect the digestive system — though headaches, fatigue, skin issues, and brain fog are also common. The most prevalent food intolerances include lactose intolerance (affecting ~68% of people worldwide), FODMAP sensitivity, histamine intolerance, and gluten sensitivity.

Food allergies involve an immune system (IgE-mediated) response and can cause severe, immediate reactions including anaphylaxis, which can be life-threatening. Food intolerances are typically non-immune digestive or metabolic reactions that develop gradually (often 2–72 hours after eating) and are generally less severe but can significantly impact quality of life. Common intolerances include lactose intolerance, histamine intolerance, and FODMAP sensitivity. Allergies require strict avoidance; intolerances often allow small amounts. This distinction matters for tracking: allergic reactions typically appear within minutes to 4 hours, while intolerance symptoms can take up to 72 hours — which is why our analysis engine uses different temporal windows for each condition.

Track any symptom that occurs after eating, even if it seems unrelated. Common food intolerance symptoms include: digestive issues (bloating, gas, diarrhea, constipation, stomach pain, nausea), skin reactions (rashes, hives, eczema flare-ups, flushing), neurological symptoms (headaches, migraines, brain fog, fatigue, dizziness), respiratory symptoms (nasal congestion, runny nose, wheezing), and other signs (joint pain, heart palpitations, mood changes, insomnia). Record the severity (mild to severe), the time it started, and any notes about what you ate in the previous hours. The more consistently you track, the faster the AI can identify patterns.

Histamine intolerance occurs when your body cannot properly break down histamine, a chemical found naturally in many foods. When histamine accumulates faster than your body can metabolize it (often due to low levels of the DAO enzyme), symptoms like headaches, migraines, digestive issues, skin rashes, flushing, nasal congestion, and heart palpitations can occur. It affects an estimated 1–3% of the population, though many cases go undiagnosed. Uniquely, histamine intolerance depends on your total body histamine load — the same food may cause symptoms one day and not the next, depending on what else you've eaten. This makes it particularly difficult to identify without systematic tracking.

High-histamine foods include aged cheeses (parmesan, cheddar, gouda), fermented products (sauerkraut, kimchi, wine, beer, kombucha), cured meats (salami, bacon, prosciutto), canned or smoked fish (tuna, anchovies, mackerel), vinegar, soy sauce, and aged leftovers. Some foods like citrus fruits, strawberries, tomatoes, and spinach can also trigger histamine release even if they don't contain high levels themselves. Histamine levels in food increase with storage time and temperature — freshly cooked food has significantly less histamine than leftovers stored for days.

Lactose intolerance is the inability to fully digest lactose, the natural sugar found in milk and dairy products. It occurs when the small intestine doesn't produce enough lactase enzyme. Symptoms include bloating, gas, diarrhea, nausea, and abdominal cramps, typically appearing 30 minutes to 2 hours after consuming dairy. It affects approximately 68% of the world's population to some degree, with prevalence varying significantly by ethnicity — from 5% in Northern Europeans to over 90% in East Asians. Note that dairy protein intolerance (casein/whey) is a separate condition with different symptoms (eczema, reflux, respiratory issues) and a much longer reaction window of up to 72 hours.

FODMAPs stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols — short-chain carbohydrates that are poorly absorbed in the small intestine. When they reach the large intestine, gut bacteria ferment them, producing gas and drawing in water, which causes bloating, abdominal pain, diarrhea, and constipation. High-FODMAP foods include garlic, onions, wheat, beans, lentils, apples, pears, and dairy products containing lactose. A low-FODMAP diet is the gold standard treatment for IBS, with up to 75% of patients experiencing symptom improvement. FODMAPs have a unique 'stacking effect' — eating multiple moderate-FODMAP foods in one day can push you over your threshold even if each food alone would be fine.

Non-celiac gluten sensitivity (NCGS) causes symptoms similar to celiac disease — bloating, abdominal pain, diarrhea, fatigue, brain fog, and headaches — but without the intestinal damage or antibodies seen in celiac disease. Unlike celiac disease (which affects ~1% of the population), NCGS is estimated to affect 0.5–13% of people. Symptoms can be delayed up to 48 hours after gluten consumption, making it difficult to identify without systematic tracking. Diagnosis is typically made by excluding celiac disease and wheat allergy, then observing symptom improvement on a gluten-free diet. Gluten is found not only in wheat, but also in barley, rye, and many processed foods (soy sauce, some sauces, beer).

Salicylate sensitivity is an adverse reaction to salicylates — natural chemicals produced by plants as a defense mechanism. They are found in many fruits (berries, grapes, oranges), vegetables (tomatoes, peppers, olives), herbs and spices (curry, cinnamon, turmeric), tea, honey, and some medications (aspirin). Symptoms range from digestive issues and headaches to skin rashes, hives, nasal polyps, and asthma-like breathing problems. It is estimated to affect 2–22% of adults with asthma.

Sulfite sensitivity is an adverse reaction to sulfites — preservatives (E220–E228) widely used in wine, beer, dried fruits, shrimp, bottled juices, and processed foods. Symptoms can include asthma attacks, wheezing, hives, headaches, and in rare cases anaphylaxis. It is most common in people with asthma, affecting approximately 5–10% of asthma patients. Sulfite reactions are typically rapid, occurring within minutes to 2 hours of consumption. Because sulfites are so common in processed foods and restaurant meals, they can be difficult to identify without careful tracking.

Nightshade sensitivity is an inflammatory reaction to plants in the Solanaceae family, which includes tomatoes, potatoes, peppers (bell peppers, chili), eggplant, and paprika. These foods contain alkaloids (solanine, capsaicin) that some people cannot tolerate. Symptoms primarily include joint pain, inflammation, stiffness, and skin rashes, often appearing 12–24 hours after consumption. While not as well-studied as other intolerances, nightshade sensitivity is commonly reported by people with autoimmune conditions like rheumatoid arthritis and inflammatory bowel disease.

Caffeine sensitivity occurs when your body metabolizes caffeine slowly (often due to genetic variants in the CYP1A2 enzyme), causing exaggerated responses to even small amounts. Symptoms include anxiety, jitters, heart palpitations, insomnia, digestive upset, and headaches. Unlike caffeine allergy (which is extremely rare), sensitivity is dose-dependent and varies widely between individuals. Some people can drink multiple cups of coffee with no issues, while others react to a single cup of tea. Caffeine is found in coffee, tea, chocolate, energy drinks, cola, and some medications.

Yes. Food intolerances can develop at any age due to changes in gut health, enzyme production, microbiome composition, stress, illness, medications (especially antibiotics and NSAIDs), or hormonal changes. For example, lactase production naturally decreases after childhood in most populations. Gut infections, surgery, or prolonged stress can also trigger new intolerances. This is why tracking food and symptoms over time is valuable — your body's reactions can change.

Irritable Bowel Syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by recurrent abdominal pain, bloating, and altered bowel habits. Food intolerances are specific adverse reactions to particular foods or food components. However, they are closely related — up to 84% of IBS patients report food-related symptoms, and many IBS symptoms are triggered by specific food intolerances (especially FODMAPs, lactose, and fructose). Identifying and managing food triggers is a key part of IBS treatment.

Unlike food allergies (which can be diagnosed with skin prick tests or blood tests), most food intolerances lack a definitive diagnostic test. The gold standard is an elimination diet followed by systematic reintroduction — removing suspected trigger foods for 2–6 weeks, then reintroducing them one at a time while monitoring symptoms. Exceptions include lactose intolerance (hydrogen breath test) and celiac disease (blood antibodies + biopsy). Tracking apps can help identify patterns before starting an elimination protocol, giving you and your healthcare provider data-driven starting points for which foods to eliminate first.

Our analysis uses a two-layer hybrid approach. First, 15 specialized rule-based detectors — each calibrated for a specific condition (histamine, FODMAPs, dairy, gluten, shellfish, peanuts, tree nuts, eggs, soy, fish, sulfites, salicylates, nightshades, caffeine, and fructose) — scan your food logs against clinically validated keyword databases and correlate them with your symptoms using condition-specific temporal windows (ranging from 2 hours for rapid allergic reactions to 72 hours for delayed intolerances). Second, Google's Gemini AI reviews the detector findings, checking for contradictions in your data and evaluating evidence strength, timing consistency, and confounding factors. This dual validation reduces false positives and ensures findings are backed by both algorithmic precision and contextual intelligence.

The app has dedicated detectors for 15 conditions: histamine intolerance, lactose intolerance, dairy protein sensitivity, gluten/celiac sensitivity, FODMAP sensitivity, salicylate sensitivity, sulfite sensitivity, nightshade sensitivity, caffeine sensitivity, fructose malabsorption, egg allergy, peanut allergy, tree nut allergy, fish allergy, shellfish allergy, and soy sensitivity. Each detector uses its own clinically calibrated parameters — including condition-specific symptom clusters, temporal windows, and confidence thresholds — rather than a one-size-fits-all approach. The system also differentiates between allergies and intolerances for the same food (e.g., dairy allergy vs. lactose intolerance) using dual-profile analysis.

Our analysis engine is built on a foundation of clinical evidence and engineering rigor. Each of the 15 detectors has parameters validated against published medical research from sources including the Mayo Clinic, the American College of Allergy (ACAAI), Food Allergy Research & Education (FARE), Monash University (FODMAP research), the Swiss Interest Group Histamine Intolerance (SIGHI), and the National Institutes of Health (NIH). The system is backed by over 900 automated tests that verify detection accuracy. Every finding goes through a dual-validation process: first by rule-based detectors, then cross-checked by Google Gemini AI for contradictions and confounding factors. Confidence levels (Low, Medium, High) are transparently reported so you always know how strong the evidence is.

Most users begin seeing meaningful pattern insights after 2–3 weeks of consistent logging (14–21 days). The AI requires sufficient data points to identify reliable correlations between foods and symptoms. For best results, log at least 2–3 meals per day and track symptoms whenever they occur. Some conditions with rapid onset (like shellfish allergy or sulfite sensitivity) may be identified sooner, while delayed-reaction conditions (like dairy protein intolerance or gluten sensitivity) need more data to establish reliable patterns.

For best results, aim to log at least 2–3 meals per day consistently. You don't need to be perfect — the AI can still identify patterns with partial data. However, more complete logging (including snacks) produces more accurate insights, especially in the first few weeks as the system learns your patterns. The app makes this easy with photo-based meal logging: just snap a picture and the AI extracts ingredients automatically.

Our detection system uses a multi-layered approach to maximize accuracy: condition-specific temporal windows (e.g., 4 hours for histamine vs. 48 hours for gluten), evidence-based confidence scoring that weighs symptom count, severity, and timing consistency, and LLM cross-validation that checks for contradictions and confounding factors. Each detector also uses a 'characteristic symptom gate' to prevent false positives — for example, the histamine detector requires at least one highly specific symptom (like flushing or hives) before reporting a finding, even if generic symptoms like headache are present. Results include transparent confidence levels so you can assess the strength of each finding.

No. Intolerance.app is not a medical device and cannot diagnose food allergies or any medical condition. It is a tracking and pattern identification tool designed to help you discover correlations in your own data. The app clearly labels all findings with confidence levels and always recommends professional validation. Think of it as a data-driven starting point for conversations with your healthcare provider — not a replacement for medical advice.

Yes. You can export your complete food diary, symptom logs, and AI analysis results in CSV or PDF format. This is particularly useful for sharing with dietitians, allergists, or gastroenterologists — giving them weeks of structured data instead of relying on memory during a short appointment.

Absolutely. We use end-to-end encryption for all health data, and your information is stored securely in GDPR-compliant servers within the EU. Your food logs and symptom data are never sold to third parties and are never used to train AI models. You maintain full ownership of your data with GDPR Article 17 compliance — you can delete your entire account and all associated data at any time from your account settings, and we confirm deletion within 30 days.