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Antihistamine Trial · Ade Whetton

Mast cell activation trial

Where the question has got to, what's still unmeasured, and a daily symptom log running across an unmedicated baseline week and the treatment period — with temperature recorded alongside, so a cooling August can't be mistaken for a drug effect.

Phase
Days logged 0
Baseline avg
Treatment avg
Adherence

Where this has got to For Dr Gemma Lewis

Written up 27 July 2026, after your message suggesting mast cell activation, possible hypermobility, and a few weeks of proper antihistamine cover.

Current plan
Cetirizine 10mg three times daily — 14 days. Prescribed by Dr Gemma Lewis, 27 July 2026. Three times the licensed dose, which is standard off-label practice for urticaria and mast cell work (guidelines support up to four times). No H2 blocker at this stage.
Dose times 06:00 / 14:00 / 22:00 — 8-hourly, mapped onto Ade's actual day.
Baseline logged 27–28 July unmedicated · treatment days 1–14 from 29 July · review 12 August.
Symptoms driving it
Heat intolerance — long-standing and marked. Gut upset — recurrent. These are the two Ade recognises without prompting.
Hypermobility (5PQ)
0–1 out of 5Below threshold
Clear no to thumb-to-forearm, dislocations, childhood contortion and self-described double-jointedness. Possible yes to hands-flat-to-floor, but limited by hamstring tightness from deconditioning rather than joint range — the least specific item on the questionnaire. Threshold is 2.
Hitchhiker's thumb
PresentDoes not score
Photographed 27 July. Distal hyperextensibility at the thumb interphalangeal joint is a common anatomical variant and is not a Beighton or 5PQ item — it is a different joint from the thumb-to-forearm sign, which is negative. Noted here so it isn't carried forward as supporting evidence.
Outstanding
A full Beighton score in person. All five Beighton manoeuvres are passive — the examiner takes the joint to end range. Self-testing consistently under-reads, because you stop where it feels odd rather than at the anatomical limit. Sixty seconds in person replaces all of the above.
Alcohol
NoneExcluded
Removes the commonest benign explanation for flushing, palpitations and gut upset.
Serum tryptase
Never doneGap
The objective limb of the diagnosis. A raised baseline would also open up hereditary alpha-tryptasemia, which fits heat and gut intolerance without needing hypermobility.
Thyroid function
Absent from the Sept 2025 panelGap
Heat intolerance, loose stools, fatigue and palpitations are also a straightforward hyperthyroid picture. Cheaper to exclude than to run a four-week drug trial around.
GGT
106 U/L (range 10–71), down from 120 in Dec 2024Unexplained
Reported as "monitoring, trending down". In a non-drinker that needs a stated cause — most plausibly metabolic, given Dec 2024 triglycerides 4.57 and HbA1c 5.7%, both since normalised (1.07 and 5.3%). Worth naming rather than assuming.
Sept 2025 panel
Total cholesterol 4.99 · LDL 2.95 · HDL 1.5 · triglycerides 1.07 · HbA1c 5.3% · BP 130/77. Cardiometabolically all in range after a substantial turnaround from Dec 2024.
Declared bias. Ade has been reading a lot about histamine and flags that this may be shaping what he notices. That's the right worry to have — mast cell activation is one of the most over-attributed labels going, and reading about it reliably produces symptoms to match. It is the reason this is built around a no-medication baseline week, objective bloods and a temperature control rather than around how he feels the trial is going. The onset section below separates what predates the reading from what doesn't.

What would help Three things

  1. One blood form: serum tryptase + thyroid function Both routine, neither delays starting the antihistamines. Tryptase isn't affected by antihistamines, so timing against the trial doesn't matter.
  2. Famotidine as the next lever if the gut doesn't shift Cetirizine at 30mg/day should cover the skin and general picture well. Gut symptoms run substantially through H2 receptors, so if everything else improves and the gut doesn't, that's the obvious next step rather than a failed trial.
  3. Beighton score in person, 60 seconds To settle the hypermobility question properly rather than on a self-scored questionnaire confounded by tight hamstrings.
If a bad flare happens at any point, that is the moment tryptase is worth repeating — the diagnostic criterion is a rise of ≥20% + 2 ng/mL within 1–4 hours of an episode, not the resting level.

Today's log

Score each domain 0–3. 0 none · 1 noticeable · 2 interfering with the day · 3 severe. Score how the day was overall, not the worst single moment.

Lie flat five minutes, take your pulse, stand up, take it again after three minutes standing still. A sustained rise of 30 bpm or more is the POTS threshold — this is the dysautonomia leg of the triad Gemma flagged, and it is the one nobody ever measures.

Doses actually taken today

DrowsinessSide effect, not a symptom — scored separately, excluded from the total
Driving. Cetirizine sedates roughly one person in ten at the licensed dose, and three times that raises the odds. Don't drive, and don't take on any driving work, until you know how a full day at 30mg actually affects you — driving while impaired by a legal medicine is still an offence. If drowsiness is a problem, that's the argument for asking Gemma about fexofenadine at an equivalent up-dose instead; it's the least sedating of the class.
Saved

Trend Total symptom score per day

Grey bars are baseline days, teal are treatment days. The amber line under each bar is that day's heat — if the teal bars only fall when the amber falls, the weather is doing the work, not the antihistamines.

Baseline Treatment Heat (peak °C)

Daily log

Onset — what predates the reading One-off

The cleanest defence against confirmation bias. Symptoms that were there long before you'd heard of any of this can't have been created by reading about it. Anything that only appeared afterwards should be treated with suspicion — by you and by Gemma. If a domain is scoring above zero in the daily log, it needs a real answer here rather than "unsure".

Mark each domain above.

Hypermobility & tryptase One-off

The 5-part questionnaire is scored on "now or ever" — joint range drops with age, so childhood counts. Two or more yes answers suggests generalised hypermobility. Pre-filled from Ade's answers on 27 July 2026; question 1 is marked yes on the generous reading.

Answer the five questions above for a score.
Ask Gemma to add serum tryptase to the next bloods. Antihistamines do not interfere with it, so timing against the trial does not matter.

Summary for Gemma Copy at end of trial

Regenerate this whenever you want the current picture. It compares baseline against treatment, adjusts for the temperature difference between the two periods, and flags if the trial is not yet long enough to read.

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