Two people can have the same skin temperature, the same heart rate, the same night of sleep — and one of them is heading into a flare. Averages hide that. Your own baseline doesn't.
The problem with "normal ranges"
Most health numbers are judged against population ranges: values that are typical across many people. Those ranges are useful for spotting outright problems, but MCAS rarely announces itself that way. The early signs of a flare are usually small departures from your typical pattern, well inside what any chart would call normal.
Learning what's typical for you
That's why MastCell Tracker focuses on change over time. As you log symptoms and collect data, the picture shifts from "is this number high?" to "is this number different for me, right now?" — a far more sensitive question.
A flare is rarely a number out of range. It's a pattern out of character.
Why it takes time — and why that's worth it
A baseline is only as good as the history behind it. The first weeks of tracking are about learning, not alerting. Consistent logging during calm stretches matters as much as logging during flares, because it's the calm that defines what a departure looks like.