An MCAS diary that finds the reactions that come later.
Bucket is an iPhone symptom and trigger diary made for MCAS (mast cell activation syndrome). Log what you met — a fragrance, a meal, a hot day, a stressful one — and how you felt. Bucket adds it up day by day and, over time, shows what tends to come before your reactions, up to about three and a half days earlier.
What people with MCAS often log.
What they met and did
Fragrance, cleaning products, smoke and chemicals
High-histamine foods, leftovers and alcohol
Heat, pollen and poor air
Long days, exercise and stress
Antihistamines and other medicines, taken or missed
How they felt
Flushing
Hives and itching
Gut upset
Brain fog
Headache
Examples of what people often track — not a list of causes or symptoms to look for. You choose what to log, and Bucket learns your own pattern.
Asked in MCAS’s own words.
When you set Bucket up, you choose every condition you have or think you might — diagnosed, suspected or still exploring. Each brings a question of its own, in words people with it use. For MCAS it’s “Overall” — settled, usual or reactive. Bucket doesn’t ask it every day, only now and then, after a heavy spell.
Your entries fill a bucket that drains over the following days, so you can see the load building. Once there’s enough in your diary, Bucket shows what tends to come before your bad days — the same day or up to about three and a half days earlier.
Pattern in your logs · example
Strong fragrance tends to be followed by flushing the next day.
9 of 12 times · 7 separate episodes · held in both halves of your data
An example of how Bucket words a pattern. It describes what tends to follow what — never what caused it.
Your bucket went near the top. Two taps help Bucket learn what matters for you — skip either.
How did you sleep?
- Badly
- OK
- Well
Overall
- Settled
- Usual
- Reactive
What Bucket does for MCAS.
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Foods counted for their histamine
Foods listed as high in histamine, or as releasing it, count for more when Bucket adds up your day — 189 foods in all, from published food lists. Leftovers count more than fresh cooking, and each age — today’s, yesterday’s, older — is watched for patterns on its own. It never tells you a food is bad for you.
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Fragrance by strength and time
A strong fragrance for an hour and a half counts for more than a passing whiff — though twice as long isn’t twice as much.
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Drinks counted twice
A drink counts its own histamine — red wine most, spirits least — and food eaten around it counts a little more.
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Scan it instead of typing it
Barcodes and ingredient labels are read for you, so a product’s contents go into your diary without typing.
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Medicines and reminders
Antihistamines and mast cell medicines with their schedules, gentle reminders, and each dose recorded as taken, missed or skipped — from your iPhone or your wrist.
Meet Shauna.
Shauna has MCAS and cares for her mum. She logs in gaps — and that’s fine.
Shauna is one of three made-up sample people built into the app, so you can try it before you’ve logged anything. A sample — not a testimonial.
Questions about Bucket and MCAS
Is there an app to track MCAS triggers and symptoms?
Yes — Bucket is an iPhone diary made for MCAS (mast cell activation syndrome). You log what you were exposed to — fragrance and chemicals, high-histamine foods and leftovers, heat, stress — and how you feel, such as flushing, hives or itching. It shows how it all adds up day to day, and looks for what tends to come before your symptoms in your own records.
Can an app find my MCAS triggers?
It can show you what tends to come before your reactions. Bucket looks through your own records for things that are followed by a symptom — the same day or up to about three and a half days later — and shows a pattern only once it has turned up many separate times. It never says something caused a reaction; that’s for you and your clinician to weigh.
Can I track high-histamine foods and reactions?
Yes — the Bucket app counts high-histamine foods such as aged cheese, cured meat and leftovers, and notes how old leftovers are. Scan a barcode or an ingredient label and a product’s contents go in without typing, then log reactions like flushing, hives or itching. It shows what tends to follow what in your own records; it never says what caused it.
Does Bucket give me a low-histamine diet?
No. Bucket never tells you what to eat or avoid. It counts foods listed as high in histamine for more when it adds up your day, and shows what tends to follow what in your own records — nothing more.
Can I log antihistamines and other MCAS medicines in Bucket?
Yes. Bucket keeps your medicines and supplements with their schedules, reminds you gently, and records each dose as taken, missed or skipped — on your iPhone or from your Apple Watch. A dose you didn’t log is never counted as missed.
Do I need an MCAS diagnosis to use Bucket?
No. Bucket asks which conditions you have or think you might — diagnosed, suspected or still exploring — and works the same either way. It never diagnoses.
How can I track reactions that come a day or two later?
Log what happens and let Bucket look back for you: it checks for things that come before a symptom anywhere from the same day to about three and a half days earlier — the delayed reactions that are easy to miss in a list. It only shows a pattern once it has turned up many separate times, still holds after allowing for your sleep and tiring days, and holds in both halves of your diary. It describes what tends to follow what; it never says what caused it.
Who wrote this.
Bucket is made by Chris, who has a connective tissue disorder and hypermobility, gets migraines, and is working towards an MCAS diagnosis through the NHS — and built Bucket to find the delayed reactions that were impossible to spot alone. Read Chris’s note.
This page describes what Bucket does. It doesn’t explain MCAS, and it isn’t medical advice. Your clinician is the place to start on what MCAS is and how it’s treated.
Checked against the Bucket app on 28 October 2026. Spotted something wrong? Tell us.
Often travels with
POTS · EDS/HSD · Migraine · Long COVID
Free, no sign-up
- Stand test Time five minutes lying and ten standing, count your pulse, print your numbers. Nothing is stored or sent.
- Try the bucket Tick what happened this week and watch a sample bucket fill and drain.
- Appointment sheet One page to fill in before you see a clinician. Print it or save it as a PDF.
- Paper symptom diary A week on one page — what you met, what you did, how you felt.
Be first to try Bucket for MCAS.
One email on launch day with the App Store link. That’s all.
Planned launch price: 30 days free, then £12.99 a month or £89.99 a year. Cancel any time in iPhone Settings.