Mast Cell Activation Syndrome (MCAS) is a condition in which mast cells—immune cells involved in allergic and inflammatory responses—release chemical mediators too easily or in excess. This can lead to a wide range of symptoms that may fluctuate over time, including flushing, hives or itching, nasal congestion, wheezing, abdominal pain, diarrhea, nausea, headaches, dizziness, rapid heart rate, fatigue, and “brain fog.” Symptoms may be triggered by things that are normally well tolerated, such as certain foods, temperature changes, stress, fragrances, infections, or hormonal shifts.

Because MCAS can affect multiple body systems and often overlaps with conditions like POTS, migraine, asthma, and hypermobility syndromes, treatment focuses on improving stability and reducing flare frequency through a combination of trigger awareness, lifestyle strategies, and individualized medication support when appropriate. While MCAS can feel unpredictable and overwhelming, many people experience meaningful improvement with a structured plan and practical tools for prevention and flare management.

Your MCAS Home Toolkit

1) Track Patterns Without Getting Overwhelmed

You do not need perfect data. You need trends.

If tracking helps, choose just 3 things:

1. Main symptom (example: flushing, diarrhea, shortness of breath)

2. Possible trigger exposure (food, heat, stress, fragrance)

3. What helped (antihistamine, rest, hydration, leaving the environment)

You can also use a 0–10 “flare intensity” score.

✅ Helpful for: identifying the top 1–3 triggers to focus on first

2) Build a “Low-Trigger” Daily Routine

Small consistency is often more effective than big changes.

Sleep stabilization

• Same wake time whenever possible

• Keep the room cool and dark

• Avoid overheating at night (common MCAS trigger)

Hydration

• Aim for steady fluids throughout the day

• Many people do better with electrolytes, not plain water alone (avoid artificial sweeteners, artificial flavors, dyes when possible)

• Dehydration can worsen dizziness, tachycardia, and headache

Temperature and environment

• Avoid hot showers, hot yoga, saunas during unstable periods

• Dress in breathable layers

• Ventilate cooking smells/steam if those bother you

Nervous system calming (MCAS and stress are connected)

A flare is not “all in your head,” but stress hormones can amplify mast cell activation.

Try:

• Longer exhales (exhale twice as long as inhale)

• Cold pack on cheeks or upper chest (briefly)

• Quiet/dim sensory environment

• Gentle stretching instead of intense exercise during flares

3) Food Strategies (Without Fear or Restriction Spirals)

MCAS food reactions are common and can be confusing. The goal is nourishment + stability, not extreme elimination.

General food principles that often help

• Eat freshly prepared foods more often when possible

• Be cautious with leftovers (histamine builds over time)

• Avoid long “empty stomach” periods if that worsens symptoms

• Choose simple meals during flares

Common higher-histamine or mast-cell triggering foods (not universal)

Some people react to:

• Alcohol (especially wine/beer)

• Fermented foods (kombucha, sauerkraut, soy sauce)

• Aged cheeses, cured meats

• Smoked/processed meats

• Vinegar-heavy foods

• Fish that isn’t very fresh

• Tomatoes, spinach, eggplant

• Citrus, strawberries

• Chocolate

You do not need to remove all of these.
Instead, consider a short “simplify and stabilize” period during frequent flares, then re-expand carefully.

Smart leftover tips (if leftovers are important for you)

• Cool food quickly after cooking

• Freeze portions right away instead of refrigerating multiple days

• Reheat from frozen when possible

4) Common OTC Medication Tools (Discuss With Your Clinician)

Many MCAS plans include a combination approach.

Do not start new medications without guidance if you have complex medical conditions, medication allergies, pregnancy, or a history of severe reactions.

Common categories:

• H1 antihistamines (for itching, hives, flushing, sneezing)

• H2 antihistamines (can help GI symptoms, reflux, flushing)

• Mast cell stabilizers (some are prescription; some supplements may help certain people)

• Leukotriene blockers (prescription in some cases)

• Nasal sprays / inhalers if asthma-type symptoms occur

✅ Tip: Many patients do best with scheduled daily prevention, not just “as needed” rescue.

5) Supplements & “Natural” Products: Use Caution

Some people benefit from certain supplements, but MCAS bodies can react strongly even to “gentle” products.

Caution with:

• New supplements started during unstable periods

• Multi-ingredient blends (hard to identify what caused a reaction)

• Essential oils, herbal tinctures, “detox” products
  
  

If you try something new:

• Start with one thing at a time

• Start low dose

• Give it several days before adding anything else

6) Reduce Chemical / Fragrance Triggers

A very common MCAS trigger is environmental exposure.

Consider:

• Fragrance-free laundry detergent

• Avoid candles, plug-ins, incense

• Fragrance-free soaps/lotions

• Masking in high-scent environments (if tolerated)

If you react at work or public places:

• Keep a “clean air” plan (step outside, car air filter, portable fan, open windows)

• Consider asking for fragrance accommodations (this is a legitimate medical need)

7) Hormones, Perimenopause, and MCAS

Many people notice worsening MCAS symptoms with:

• Perimenopause

• PMS/PMDD

• Ovulation shifts

This is not “in your head.” Hormones can affect immune signaling and inflammation.

Helpful steps:

• Track your symptom trends across your cycle if relevant

• Build extra rest/recovery during predictable flare windows

• Talk with your clinician if symptoms are consistently cyclical

MCAS Flare Plan (Step-By-Step)

Step 1: Remove the trigger if possible

• Stop the new food / supplement

• Leave the environment (heat, fragrance, smoke)

• Pause exertion

• Cool down (cool air, cold pack briefly, hydration)

Step 2: Use your approved rescue plan

Follow your personalized plan from your clinician.

Step 3: Support the body for 12–24 hours

• Fluids + electrolytes

• Simple tolerated meals

• Rest, low sensory stimulation

• Avoid alcohol and intense exercise

• Avoid new foods/supplements until stable again

• Make a plan with your provider to take added antihistamines or other medications
  
  

Step 4: Document what happened (briefly)

Just enough to learn:

• What was the likely trigger?

• What helped?

• How long did it last?

When MCAS Symptoms Are an Emergency

Call 911 or seek emergency care if you have:

• Trouble breathing, wheezing, or chest tightness that is worsening

• Throat swelling, voice changes, difficulty swallowing

• Lip/tongue swelling

• Fainting or severe dizziness

• Severe weakness or confusion

• Rapidly spreading hives with systemic symptoms

• Symptoms consistent with anaphylaxis

If you have been prescribed an epinephrine auto-injector, use it as directed and call emergency services.

What to Avoid During Unstable MCAS Periods

During frequent flares, try to avoid:

• Alcohol

• Overheating

• Intense workouts

• Trying multiple new foods at once

• Starting several new supplements at once

• Skipping meals + dehydration

• High stress without recovery time

What Helps Most People Long-Term

Most patients improve when they focus on:

1. A consistent daily routine (sleep, meals, hydration)

2. Reducing trigger stacking

3. Scheduled preventive medications (if recommended)

4. Avoiding “all-or-nothing” restriction

5. Building a realistic flare plan

6. Identifying the top 1–3 triggers rather than chasing every possibility

A Supportive Note

MCAS can feel unpredictable, isolating, and scary — especially if symptoms mimic panic or cause sudden body changes like flushing, fast heart rate, or shortness of breath.

You deserve care that is:

• trauma-informed

• grounded in safety

• collaborative

• not dismissive
  
  

If you feel like your symptoms are changing, worsening, or limiting your daily life, please schedule a visit so we can adjust your plan and make sure other conditions are not being missed.