Mast Cell Activation Syndrome (MCAS)

What is MCAS?

Mast cells are immune/defense cells found throughout the body, normally sitting quietly in the tissues sensing for assaults, whether infectious, environmental, or otherwise. When triggered, they can react explosively, producing and releasing into the tissues (and even the circulation) a wide range of potent chemical signals called mediators, each of which has a vast array of effects on other cells and tissues to help the body resist and recover from the assault.

We’ve known about some types of mast cell activation diseases — the tip of the iceberg — for a long time: allergies and other allergic-type problems, and the rare disease of mastocytosis which features not only inappropriate mast cell activation but also excessive (cancerous) mast cell growth. In the last decade, we’ve begun to learn there are a variety of other patterns of inappropriate mast cell activation, causing an array of clinical illnesses we now are collectively terming mast cell activation syndrome (MCAS).

Mast cell activation syndrome (MCAS) is increasingly appearing to be the bulk of the iceberg of mast cell activation diseases (MCAD), all of which share the common theme of inappropriate mast cell activation.

MCAS causes chronic inflammation in multiple organs/tissues/systems, with or without allergic-type problems and sometimes even abnormal growth and development in various tissues, and there can be acute flares (“spells”) of symptoms from time to time as well. Although its variability in clinical presentation can make it difficult to initially recognize MCAS as the underlying/unifying root of the typical patient’s many ills, we are increasingly recognizing MCAS is a common problem.

Fortunately, even though MCAS is not presently curable, there are many treatments known to be helpful for controlling the disease, and most patients accurately diagnosed with it can get significantly better even if they have been suffering for decades.

MCAS is not a new disease but rather a newly recognized disease, and there are no health professional schooling/training programs yet providing students/trainees any significant formal education about MCAS, a deficiency which likely will take years to a few decades to correct.

Dr. Tania Dempsey
Dr. Lawrence Afrin

Drs. Dempsey and Afrin are committed to furthering our knowledge and understanding of MCAS and to this end they generously provide educational opportunities through lectures, conferences, and publications with the hope that these efforts will eventually lead to medical schools and other training programs to include MCAS in their curriculum.

“If an MCAS patient visits a doctor and the doctor doesn’t learn something new about the disease from that visit, then the doctor hasn’t paid enough attention.” – Dr. Lawrence Afrin

Clinical Care

The AIM Center team is internationally recognized for its approach, research, and care in the MCAS space.

For an Appointment, Please contact our office

Mast cell triggers may include:


  • Heat, cold or sudden temperature changes
  • Stress: emotional, physical, including pain, or environmental (i.e., weather changes, barometric pressure, EMF, pollution, pollen/pet dander, etc.)
  • Exercise
  • Fatigue/sleep deprivation
  • Food or beverages, including alcohol
  • Medications (opioids, NSAIDs, antibiotics and some local anesthetics) , excipients, vaccines, and contrast dyes
  • Natural odors, chemical odors, perfumes and scents
  • Sun/sunlight
  • Head trauma
  • Venoms (bee, wasp, mixed vespids, spiders, fire ants, jellyfish, snakes, biting insects, such as flies, mosquitos and fleas, etc.)
  • Infections (viral, bacterial or fungal)
  • Mycotoxins
  • Microbiome changes (small intestinal bacterial overgrowth, dysbiosis
  • Mechanical irritation, friction, vibration
  • Implants and metal exposure: amalgam, heavy metals, orthopedic implants, mesh, silicone
  • Hormones

Did you know?

Research estimates that 17-20 percent of the US population have MCAS, which is one out of every six to seven people.