What is MCAS?

Mast cell activation syndrome (MCAS) is one type of mast cell activation disorder (MCAD), and is an immunological condition in which mast cells are inappropriately activated, resulting in a range of chronic symptoms across various systems including: neurological, central nervous system, dermatological, rheumatological, cardiovascular, musculoskeletal, GI Tract, urinary tract, and immune system.

What is/are MCAD?

  • Umbrella term for the full realm of Mast Cell Activation Disorders
    • Mastocytosis (rare disease)
    • Allergies, Urticaria, Angioedema, Anaphylaxis
    • Inappropriate activation of the Mast cells


  • Possible to see any and all systems in the body affected
  • General themes include inflammation and allergic reactions
  • Can manifest as a wide range of symptoms
    • Neurological: fatigue, motor and sensory, irritability, brain fog
    • Central nervous system: depression, anxiety
    • Dermatological: rash, flushing, hives, runny nose, issue with hair, teeth, nails
    • Rheumatological: joint pain
    • Cardiovascular: autonomic, tachycardia, variable heart rate, blood pressure, palpitations
    • Musculoskeletal: pain, osteopenia, osteoporosis
    • GI Tract: reflux, nausea, diarrhea, constipation
    • Urinary tract: irritation, pain, inflammatory problems
    • Immune system: increased susceptibility to infection, risk for malignancies, autoimmune disease
    • And more…

What causes it?

  • Many different possibilities
    • Mast cells overreacting
    • Assorted mutations
    • More research is needed


Questionnaire – a validated questionnaire can be obtained from this study.

  • Basic/preliminary screen: Histamine plasma, Chromogranin A, Tryptase (can be done using LabCorp).  If two tests are positive = MCAS
  • MCAS Questionnaire filled out by patient and by doctor.
    • Score between 8-14 = suggestive of MCAS, score above 14 = highly suggestive.  Either score indicates you should continue looking for MCAS.
    • If score is below 8, consider other similar conditions; Lyme disease, environmental allergen/exposures

Natural and OTC Medication Treatments

  • Afrin has found identifying dietary and environmental triggers and avoiding them to be very helpful
  • Low Histamine diet
  • Low FODMAP diet
  • Glutamine, shown to lower HI
  • Probiotics
  • Treatment of dysbiosis, SIBO
  • Natural anti-histamines
  • Vitamin C, B6
  • DAO enzymes
  • Identify an OTC H1 blocker and H2 blocker that works for you
  • Non-sedating H1 blockers (preferred)
    • Claritin, Zyrtec, Allegra, Xyzal
  • Sedating H1 blocker
    • Benadryl
  • H2 blockers
    • Pepcid, Zantac, Tagamet, Axid
  • Cromolyn is good for digestive involvement, because it’s not absorbed. Might be most effective for GI
    • Comes in various forms: oral, eye drops, nasal, nebulizer, cream

Time and Dose

  • A month at most to clearly notice effect; if not, move on to trying a different medication
  • Follow the dosing listed on label at first, but often for MCAS patients it’s best to take twice per day. You could experiment with higher dose for 2-3 weeks, but if it doesn’t clearly help, then reduce dose. Do not take anymore than is beneficial
  • Best practice, start with less expensive drugs first

Research to support?

Learn More