Why a checklist helps
MCAS is multi-system by definition. That makes it easy to walk into a 10-minute appointment, mention three things, and have each treated separately — flushing as "just stress", IBS as "just diet", palpitations as "just anxiety". The international consensus criteria specifically require multi-system involvement, so the pattern matters more than any one symptom.
This checklist isn't diagnostic. It's a way to lay out the pattern in front of your GP so they can decide whether immunology referral is warranted.
Symptoms by body system
Skin and mucosa.
- Flushing (sudden warmth and redness of face, chest, neck).
- Itching with or without rash.
- Urticaria (hives) or angioedema (lip, eyelid or tongue swelling).
- Dermographism (skin writing — line raises when scratched).
- Burning or stinging skin.
Gastrointestinal.
- Cramping, bloating, nausea.
- Diarrhoea, sometimes alternating with constipation.
- Reflux, food intolerances that change over time.
Cardiovascular.
- Palpitations, tachycardia (high heart rate), POTS-type symptoms on standing.
- Sudden drops in blood pressure, pre-syncope or fainting.
Respiratory.
- Nasal congestion, sneezing fits.
- Wheeze, throat tightness, sensation of a closing throat (red flag — see below).
Neurological / cognitive.
- Headaches, brain fog, fatigue out of proportion to activity.
- Tingling, dizziness.
Reproductive / endocrine.
- Symptoms cycling with menstrual cycle.
- Increased symptoms in perimenopause.
Common triggers
- Heat (hot showers, hot weather, exercise warmth).
- Alcohol — especially red wine, beer, anything fermented.
- Certain foods, particularly histamine-rich (aged cheese, leftovers, tomatoes, cured meat).
- Stress and lack of sleep.
- Specific medications — NSAIDs, opioids, contrast dye, some anaesthetics.
- Strong smells (perfume, cleaning products).
Red flags — don't wait
Anaphylaxis is a medical emergency. If you have throat tightness, breathing difficulty, swelling, sudden severe drop in blood pressure, or loss of consciousness — use an adrenaline auto-injector if you have one and call 999. Don't wait to see if it passes.
What to bring your GP
The most effective way to use this checklist:
- Tick the symptoms you've had in the last 12 months.
- For each one, note frequency (daily, weekly, monthly) and at least one trigger if you've identified one.
- Take a single-page printout to the appointment. Ask for it to be added to your notes.
- Ask specifically: "Given this multi-system pattern, can you refer me to immunology to consider MCAS against the international consensus criteria?"
Full pathway in our MCAS UK diagnosis guide. If your GP won't refer, a formal NICE-cited letter that names the consensus criteria and the pattern of multi-system symptoms is usually what unlocks it. Finally Seen writes that letter for £49.
Frequently asked questions
›Is this checklist a diagnosis?
No. MCAS is a clinical diagnosis made by an immunologist or allergist against international consensus criteria, not a checklist. The checklist is a way to organise your symptoms so a GP can decide whether referral is warranted.
›What's the difference between mast cell activation and an allergy?
A classic allergy is an IgE-mediated reaction to a specific allergen. MCAS is a broader pattern of inappropriate mast cell mediator release across multiple body systems, often triggered by many seemingly unrelated things (heat, stress, alcohol, foods, medications).
›Do I need a positive tryptase test?
Not necessarily. The international consensus criteria require multi-system symptoms, objective evidence of mast cell mediator release (which can include a rise in serum tryptase during/after a reaction), and response to mast cell-targeted treatment. Baseline tryptase can be normal in MCAS.
›Which symptoms are red flags I shouldn't wait on?
Throat tightness, swelling, breathing difficulty, fainting, or a sudden drop in blood pressure are anaphylaxis red flags — call 999. Persistent unexplained weight loss, GI bleeding, or new neurological symptoms also need urgent assessment regardless of suspected MCAS.