---
title: Mast Cell Activation Syndrome
description: Mast cell activation syndrome causes mast cells to overreact & release chemicals when they shouldn’t. It's hard to diagnose and treatment response varies.
image: https://www.fxmedresearch.org/hubfs/FMRTC%20Blog%20Photos/Mast%20Cell%20Feature.jpg
---
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# Mast Cell Activation Syndrome
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## Mast Cell Activation Syndrome
Mast cells are a type of immune cell that originates in the bone marrow and are found in most tissues. They play a role in both health and disease, and are most commonly known for their role in atopic disorders (allergies) and anaphylaxis. When they’re functioning normally, mast cells release chemicals that help protect the body—they’re like first responders for the immune system. But when they’re not properly regulated, mast cells can degranulate and dump their chemical mediators too easily, causing havoc across the body in a condition called mast cell activation syndrome (MCAS). Mast cells have been linked to several chronic allergic/inflammatory disorders, autoimmune diseases, and cancers. Some people with MCAS develop a histamine intolerance.
If someone has mast cell activation syndrome, the mast cells overreact and release chemicals when they shouldn’t. Often, they erroneously see food, fragrances, temperature, and even stress as something to “defend against.” Depending on which chemical the mast cells release, people can experience a whole range of symptoms, including hives, diarrhea, shortness of breath, anxiety, fatigue, brain fog, congestion, lightheadedness, and much more. MCAS may even cause anaphylaxis, a medical emergency. It may pop up in people who have Ehlers-Danlos Syndrome (EDS), a connective tissue disorder, Postural Orthostatic Tachycardia Syndrome (POTS), myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), long COVID, or Lyme disease, among others.
MCAS is difficult to diagnose and treatment response varies. Finding the root cause or trigger is key. If someone has MCAS, it is important to identify and avoid substances and environments that provoke the symptoms. If a severe anaphylactic reaction occurs, call 911 right away—emergency treatment will be needed with epinephrine. Natural and pharmaceutical antihistamines, mast cell stabilizers, and supplements can help. Steroids are also used to help treat the symptoms.
The mast cells are just trying to do their job and keep the body safe, but as is often the case, the immune system can lose its natural checks and balances and may need help getting back on track.
### Resources
- The American Academy of Allergy Asthma & Immunology. Mast Cell Activation Syndrome. [https://www.aaaai.org/conditions-and-treatments/related-conditions/mcas](https://www.aaaai.org/conditions-and-treatments/related-conditions/mcas)
- Immunology and Allergy Clinics of North America. Mast cell mediators in allergic inflammation and mastocytosis. [https://www.ncbi.nlm.nih.gov/pubmed/16931289 ](https://www.ncbi.nlm.nih.gov/pubmed/16931289)
- International Archives of Allergy and Immunology. Definitions, criteria and global classification of mast cell disorders with special reference to mast cell activation syndromes: a consensus proposal. [https://www.ncbi.nlm.nih.gov/pubmed/22041891 ](https://www.ncbi.nlm.nih.gov/pubmed/22041891)
- International Archives of Allergy and Immunology. Prevention of mast cell activation disorder-associated clinical sequelae of excessive prostaglandin D(2) production. [https://www.ncbi.nlm.nih.gov/pubmed/18622141 ](https://www.ncbi.nlm.nih.gov/pubmed/18622141)
- New England Journal of Medicine. Mast Cells, Mastocytosis, and Related Disorders. [https://www.ncbi.nlm.nih.gov/pubmed/26154789 ](https://www.ncbi.nlm.nih.gov/pubmed/26154789)
- International Journal of Infectious Disease. Mast cell activation symptoms are prevalent in Long-COVID [https://doi.org/10.1016/j.ijid.2021.09.043](https://doi.org/10.1016/j.ijid.2021.09.043)
- [Immune](https://www.fxmedresearch.org/blog/tag/immune),
- [Mast Cell](https://www.fxmedresearch.org/blog/tag/mast-cell),
- [Mast Cell Activation Syndrome](https://www.fxmedresearch.org/blog/tag/mast-cell-activation-syndrome),
- [MCAS](https://www.fxmedresearch.org/blog/tag/mcas)
## [Sunjya Schweig](https://www.fxmedresearch.org/blog/author/sunjya-schweig-1)
Dr. Schweig is an expert in complex chronic illnesses which require rigorous investigation and management. He has been studying, teaching, and practicing integrative and functional medicine for over 25 years. As Founder and President of the California Center for Functional Medicine (CCFM), and the Functional Medicine Research and Technology Center, Dr. Schweig believes that an individualized, data-driven, precision medicine approach is fundamental for managing patients with chronic illness.
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