Guide · 4 min read · Aug 13, 2026
How to track a food intolerance
Something you're eating might be causing how you feel. So you start paying closer attention: what you ate, how your stomach felt after, whether today was a bad day.
A week later you can't remember if the headache came before or after the yogurt, and the pattern, if there was one, is gone. Here's how to track it in a way that actually holds up.
Why "just paying attention" doesn't work
Memory isn't built for this. You need to compare dozens of meals against dozens of symptoms, spread across weeks, to see something that isn't a coincidence. Most people can hold a day or two of that in their head. By day five, without something written down, the details blur together and the whole effort gets abandoned.
It's also not usually one meal, one reaction. Some reactions show up hours later, sometimes the next day. If you're relying on "did I just eat something weird," you'll miss the exposures that happened the night before.
What to actually log
You don't need a perfect diary. You need enough data points to see a pattern. Three things matter:
- Meals, with real ingredients. "Lunch" tells you nothing later. "Chicken wrap, hummus, iced coffee" does.
- Symptoms, as they happen. Bloating, headache, fatigue, skin reactions, whatever shows up. Log it close to when it happens, not from memory that evening.
- Stools, if it's a digestive issue. Consistency and timing matter more than most people expect.
Timing matters more than detail. A rough log taken in the moment beats a detailed one written from memory that night.
How long before a pattern shows up
One bad afternoon after eating dairy doesn't prove anything. You're looking for something that repeats: the same ingredient showing up before the same reaction, more than once, across a couple of weeks. Give it time before you draw any conclusions. A single data point is a coincidence. A pattern is several.
Bring the data, not the guess, to your doctor
"I think it might be dairy, maybe" is hard for a doctor to act on. "Here are twelve days of meals, symptoms, and timing, and dairy shows up before most of my bad days" is a real starting point for a conversation.
You're not trying to diagnose yourself. You're trying to walk in with something concrete instead of a vague complaint.
A faster way to do it
This is exactly what BellyMystery is built for. Logging a stool takes under 15 seconds. Logging a meal, even with a photo, takes under 30. Everything saves to your phone right away, no waiting on the internet. As entries build up, the app looks for correlations between what you ate and how you felt, and shows you the pattern in plain English, framed as something worth discussing with a doctor, never as a diagnosis.