Food and symptom log for histamine intolerance

The idea

Histamine intolerance has no reliable test, so patients are told to run elimination diets and keep a diary, then handed a photocopied food list. The cruel part is the time lag: a reaction can arrive 30 minutes or 24 hours after the trigger, which makes eyeballing a paper diary nearly useless. People spend months suspecting the wrong foods.

Generic food diaries cannot do the two things that matter here: know each food’s histamine profile, and correlate across lagged windows. Shipping the SIGHI compatibility list inside the app and running weekly lag-aware correlation turns a diary into a suspects list, which is the actual job the patient is trying to do.

Who pays

The buyer is a patient who has already spent thousands on specialists and elimination-diet false starts, and demonstrably pays for 8-dollar PDF food lists on Etsy. Price at 8 dollars a month after a 14-day trial via RevenueCat. Distribution: r/HistamineIntolerance and r/MCAS, histamine-focused dietitians and Instagram educators, and SEO on low histamine foods list queries with a free food browser as the front door.

MVP scope

• Food logging with built-in SIGHI ratings, search and barcode entry
• Symptom log with severity, plus daily context (sleep, stress, meds)
• Weekly time-lagged correlation report with ranked suspects and plain-language confidence
• PDF export of diary and report for the allergist appointment
• Sync via Supabase, paywall via RevenueCat
• Skip for v1: other intolerances (FODMAP, salicylates), meal photos with AI recognition, community features, wearable heart-rate import

Build HistaLog, a React Native (Expo) app for people with histamine intolerance or MCAS who are running their own elimination diets.

Ship with the SIGHI food compatibility list built in as a local database: each food carries the SIGHI rating 0-3 plus flags (liberator, DAO blocker). Food entry is search-first with the SIGHI badge shown inline; support Open Food Facts barcode scan mapped to the nearest SIGHI entry, with a clearly-labelled unmatched state rather than a guess. Meals log multiple foods with portion sizes and a timestamp.

Symptom log: user picks from a customisable symptom list (flushing, hives, headache, GI, tachycardia, congestion) with severity 1-10 and timestamp. Also log daily context: sleep quality, stress, medications, antihistamine or DAO taken.

The differentiator is time-lagged correlation. Weekly, compute correlation between each food (and each SIGHI category) and symptom onset across lag windows of 30 min, 2 h, 6 h, and 24 h, controlling for antihistamine days. Present as a ranked suspects report with plain-language confidence (strong signal, weak signal, not enough data), minimum 3 exposures before a food can appear. Include a clear this-is-not-medical-advice frame and a PDF export for the allergist.

Screens: Today timeline, Add Food, Add Symptom, Weekly Report, Foods browser, Settings.

Stack: Supabase (auth, sync), RevenueCat paywall: 14-day trial, then 8 dollars per month.