Disclaimer

This article is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional regarding your individual medical concerns. MCAS is a complex condition that requires medical evaluation and individualized treatment.

What Is MCAS?

Mast Cell Activation Syndrome (MCAS) is a condition in which mast cells become overly reactive and release excessive amounts of inflammatory chemicals, often inappropriately or in response to triggers that would not normally cause a significant reaction.

Mast cells are immune cells found throughout the body, especially in:

Skin
Respiratory tract
Gastrointestinal tract
Blood vessels
Connective tissues
Nervous system

Their job is to protect us from infection, parasites, toxins, and injury. They act as “first responders” in the immune system.

When functioning normally, mast cells release chemical messengers only when needed. In MCAS, they can release these chemicals too frequently, too intensely, or at inappropriate times.

What Do Mast Cells Release?

Mast cells contain hundreds of biologically active substances, including:

Histamine
Tryptase
Prostaglandins
Leukotrienes
Cytokines
Heparin

These chemicals affect:

Blood vessels
Digestion
Heart rate
Blood pressure
Breathing
Pain signaling
Temperature regulation
Brain function

This is why MCAS can affect nearly every body system.

Why Does the Body Do This?

Researchers do not yet have a complete answer.

Current theories include:

Genetic Predisposition

Some people appear genetically prone to having more reactive mast cells.

Connective Tissue Differences

Changes in connective tissue may influence how mast cells behave and communicate with surrounding tissues.

Immune Dysregulation

The immune system may become overly sensitive after:

Viral infections
Chronic inflammation
Environmental exposures
Physical trauma
Significant stressors

Nervous System Involvement

Mast cells communicate directly with the nervous system.

When the autonomic nervous system becomes dysregulated, mast cells may become easier to trigger.

How Do People Get MCAS?

MCAS is generally not considered something you “catch.”

Rather, it appears to develop through a combination of:

Genetics
Immune system susceptibility
Environmental triggers
Infections
Hormonal changes
Physical or emotional stress

Many people report symptoms worsening after:

Viral illnesses
Surgery
Pregnancy
Major stress
Significant injuries

What Are Common Symptoms?

Symptoms vary dramatically from person to person.

Skin

Hives
Itching
Flushing
Rashes
Dermatographia (“skin writing”)

Respiratory

Wheezing
Shortness of breath
Nasal congestion
Throat tightness

Cardiovascular

Rapid heart rate
Palpitations
Lightheadedness
Blood pressure fluctuations
Fainting

Gastrointestinal

Nausea
Reflux
Diarrhea
Abdominal pain
Bloating

Neurological

Brain fog
Headaches
Migraines
Anxiety
Dizziness

General

Fatigue
Temperature intolerance
Chemical sensitivities
Medication sensitivities

Severe Reactions

Some individuals experience episodes resembling allergic reactions or even anaphylaxis despite no obvious allergy trigger.

Common Triggers

Triggers are highly individual but may include:

Heat
Cold
Exercise
Stress
Infections
Fragrances
Smoke
Alcohol
Certain medications
High-histamine foods
Hormonal fluctuations

A trigger that affects one person may not affect another.

Why Is MCAS Associated with Hypermobility?

One of the most discussed relationships in recent years is the overlap among:

Hypermobile Ehlers-Danlos Syndrome
Hypermobility Spectrum Disorder
Postural Orthostatic Tachycardia Syndrome
MCAS

Researchers continue to investigate why these conditions frequently occur together.

Proposed explanations include:

Mast Cells Live in Connective Tissue

Mast cells are abundant within connective tissues.

Since connective tissue is altered in hypermobility disorders, mast-cell behavior may also be affected.

Blood Vessel Effects

Histamine causes blood vessels to dilate.

This can worsen symptoms commonly seen in POTS and dysautonomia, including:

Dizziness
Tachycardia
Blood pooling
Fatigue

Nervous System Interaction

Mast cells and the autonomic nervous system constantly communicate.

Both dysautonomia and MCAS involve disruptions in these regulatory systems.

Shared Genetic Factors

Researchers suspect there may be overlapping genetic and biological pathways, though definitive answers remain under investigation.

How Is MCAS Diagnosed?

Diagnosis can be challenging.

Typically, physicians look for:

Symptoms involving multiple body systems
Evidence of mast-cell mediator release
Improvement with mast-cell-targeted treatments

Testing may include:

Serum tryptase
Urinary histamine metabolites
Urinary prostaglandin metabolites

Because mast-cell mediators fluctuate, normal testing does not always rule out MCAS.

Who Treats MCAS?

Depending on symptoms, care may involve:

Allergists/Immunologists
Gastroenterologists
Cardiologists
Dermatologists
Neurologists
Primary care physicians familiar with mast-cell disorders

Many patients ultimately require a team approach.

Can MCAS Be Fixed?

Currently, there is no universally accepted cure.

Treatment focuses on reducing symptoms, minimizing triggers, and stabilizing mast cells.

Common approaches include:

Trigger Management

Identifying and avoiding triggers when possible.

Medications

Under physician supervision:

H1 antihistamines
H2 antihistamines
Mast-cell stabilizers
Leukotriene inhibitors

Lifestyle Support

Stress management
Sleep optimization
Hydration
Electrolyte support
Pacing activities

Nutritional Strategies

Some individuals benefit from temporary reduction of high-histamine foods under guidance from knowledgeable healthcare professionals.

Why Massage Therapists Should Know About MCAS

Clients with hypermobility frequently report symptoms suggestive of mast-cell dysfunction.

A therapist may notice:

Flushing during treatment
Unexpected reactions to lotions or essential oils
Heat intolerance
Chemical sensitivities
Unusual post-treatment fatigue
Dizziness when changing positions

Understanding MCAS can help therapists:

Modify environmental triggers
Reduce overwhelming sensory input
Adjust heat applications
Pace treatments appropriately
Improve client safety and comfort

Experts and Organizations to Cite

For educational materials, consider citing:

The Mast Cell Disease Society (TMS)⁠
The Ehlers-Danlos Society⁠
Lawrence Afrin
Anne Maitland
Cem Akin

Key Takeaway

MCAS is a disorder of mast-cell overactivation that can affect nearly every body system. While researchers are still uncovering exactly why it occurs, it appears to overlap significantly with hypermobility disorders, dysautonomia, and related connective tissue conditions. For people with hypermobility, understanding mast-cell dysfunction may help explain symptoms that otherwise seem unrelated—from hives and digestive issues to rapid heart rate, fatigue, and medication sensitivities.

Jennifer Richards, LMT
Educating massage therapists about hypermobility, connective tissue disorders, and client safety.