Tools for living with MCAS

Plan for better days.

Mast Cell Decoded builds practical tools to help people living with mast cell activation syndrome spot their patterns, plan around their triggers, and have more good days.

Try the free forecast About the project
“I used to spend a whole day wondering what set me off. Now I open the diary, look at the week, and usually have a pretty good guess.”
Rachel M. Living with MCAS since 2019
“The forecast is the first thing I check in the morning. On a low-score day I keep plans light, and I have fewer bad surprises.”
Daniel K. Diagnosed in 2022
“I walked into my allergist appointment with the Doctor Summary printed out. For once we talked about patterns, not just how I felt that week.”
Priya S. Health Diary subscriber
“Closing a case at night, even with a guess, lets me stop replaying the day in my head.”
Megan T. Mom of two, MCAS since 2020
“Pressure drops wreck me. Seeing one coming two days out means I can pre-medicate instead of scrambling.”
Luis R. Living with MCAS and EDS
“My medicine cabinet used to be a drawer of half-remembered bottles. Now it's one list I can actually show my doctor.”
Hannah W. Diagnosed in 2021
“It's built by someone who gets it. Nothing is loud or alarming, and it never makes me feel like a bad day was my fault.”
Jordan P. Living with MCAS since 2018
“Three months of logging showed my worst days lined up with high-histamine leftovers. I'd never have spotted that on my own.”
Sam L. Health Diary subscriber
“I log from my phone in about ten seconds. If it took longer I'd never keep it up, especially on a flare day.”
Aisha N. Diagnosed in 2023
“My husband checks the forecast too now. When it's a rough one, he just quietly takes on more that day.”
Claire B. Living with MCAS since 2017
“Discoveries is where I keep what I've learned. Some hunches turned out to be wrong, and that's useful to know too.”
Tom H. Living with MCAS and POTS
“My new specialist read the summary and said it saved us half the appointment.”
Erin D. Health Diary subscriber
“Spring used to blindside me every year. This year I watched the pollen climb and had a plan before it hit.”
Marcus J. Diagnosed in 2022
“Asking Claude what my hard days had in common this month felt like having a research assistant for my own body.”
Nina F. AI Connector user
“The free forecast alone was worth signing up for. The diary is what made me stay.”
Grace O. Subscriber since the beta

The tools

Tools for better days

Check what the day may bring, keep track of how you feel and what you take, and walk into your next appointment with it all on one page.

Weekly Forecast

A score from 0 to 100 each day for five known and suspected MCAS triggers, with a plain-English note on what's driving it.

Open the forecast →

Health Diary

Log how you feel, when you flare, your daily measurements and supplements in seconds, right next to each day's forecast.

Open the diary →

Medicine Cabinet

Keep track of your supplements and medications: what works for you, what doesn't, and what you think you'll try next.

Open the cabinet →

Doctor Summary

Your supplements, medications, flares, symptoms and medical events on one printable page, ready for your appointment.

Open the summary →

Detective Cases

Every flare or rough day opens a case. Name the likely culprits, and see what's behind your hard days over time.

Open your cases →

Health Notes

Keep track of your symptoms, what you've figured out, and the lab findings you don't want to forget.

Open your notes →
New

AI Connector

Connect Claude or another AI assistant to your diary, and ask it about your days, flares and cases in plain words.

Connect your AI →
Free week Sign up and try every tool free for a week, the full forecast and Health Diary included. No card needed. Start free →

From the blog

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Humble beginnings

It started with a diary

Mast Cell Decoded began with a symptom diary and a nagging question: do the rough days line up with something in the air? Tracking pollen, smoke, pressure swings and more by hand wasn't realistic, so we built a forecast that does it for you. It's only the first step, and more tools are on the way.