An IBS food and symptom diary for iPhone.
Need help? Email engr.kamalnasir@gmail.com. Every message is read and answered by the developer, usually within a couple of days.
Because it does not. Before Fennel reports that symptoms followed a food, it needs a minimum number of days you actually ate that food, a minimum number of days you did not, and enough symptom episodes to compare against. Below that, a difference between two small numbers is noise, and reporting it would be inventing a trigger. The screen shows how far along you are instead, for example that two more garlic days would reach a reading. The category's most quoted failure is an app telling somebody their number one trigger was water, and these thresholds are exactly what prevents that.
Because it cannot know, and because that framing is what makes food tracking miserable. Fennel counts what you logged and reports how often symptoms followed a food or a FODMAP group, with the sample sizes and the time window shown beside every number. It never labels a food, never colours one red or green, and never tells you to avoid anything. Colour in this app marks how much evidence there is, and nothing else. What to do about a pattern is a conversation for you and your clinician or dietitian.
Realistically, a few weeks of regular logging before individual foods have enough behind them. Group patterns and context factors such as sleep and stress usually reach their thresholds sooner, because they occur more often. The trigger screen is readable from day one and honest about being empty.
Published, openly available sources, listed on the Sources page and linked from inside the app on the screen that makes the claim. Where the sources disagree or do not cover a food, Fennel leaves it untagged rather than guessing.
Bookkeeping for challenge days and rest days, run with your dietitian. It schedules the days, records what you logged on them, and drafts a reading you can accept or overrule. It is not a prescription and it does not decide anything for you. The phase lengths are shown as ranges because the sources state them as ranges.
Yes. The food information and every calculation are on your device. There is no account and no server.
Yes, and it is free and always will be. Settings, then Export your data, writes everything you have logged as a CSV file you keep. Charging for a copy of your own diary is the thing this app is positioned against.
Fennel shows one card suggesting you discuss it with a clinician, and cites where that suggestion comes from. It will not tell you what it might mean. Please take that card seriously and speak to someone.
Subscriptions are managed by Apple: open Settings on your iPhone, tap your name, then Subscriptions. To restore a purchase on a new device, open Settings inside Fennel and tap Restore. Logging, the day timeline, the calendar, CSV export and the app lock were never behind the purchase and keep working either way.
Fennel is made by an independent developer. Last updated 30 August 2026.