What is Mast Cell Activation Syndrome (MCAS)?
- Dr. Thalia

- Jul 25, 2020
- 3 min read
Updated: Aug 12, 2020

Mast cells are immune cells that release histamine and are involved in allergic reactions. They are absolutely necessary to our immune system, but can overreact when triggered by stressors including infections and inflammation. Mast cells have the highest concentration in the areas of our body that interact with the outside world: our skin, lungs and digestive system.
Mast cells are patrolling for inflammatory external offenders and create inflammation to help protect us. Mast cell overactivation in response to stressors including infections and stress can contribute to chronic and uncomfortable symptoms:
Symptoms of Mast Cell Activation Syndrome and/or histamine intolerance are multi-systemic and can include:
Anxiety
Blood sugar instability (a.k.a. Hangry)
Depression
Extreme reactions to insect bites
Fatigue
Gastrointestinal Issues like abdominal pain, diarrhea, bloating, nausea, vomiting
Headaches
Head pressure
Heart palpitations
Hives
Joint and muscle pain
Lightheadedness with standing
Nasal congestion
Pain with urination
Skin itching
Urinary frequency
Conditions Mast Cell Activation Syndrome may be related to include:
Allergies
Asthma
Chronic Hives
Chronic Inflammatory Response Syndrome
Crohn’s disease and Ulcerative Colitis
Fibromyalgia
Gastroesophageal Reflux (GERD)
Hypermobility Syndromes like Ehlers Danlos Syndrome
Interstitial Cystitis
Migraines
Leaky Gut Syndrome
Treatment for MCAS
While we do not currently know all of the causes for MCAS, there are effective ways of controlling it. Reducing and aggressively managing the inflammation involved in MCAS is a critical first step before treating chronic infections. Bringing down environmental (e.g. inflammation from food) helps to open the doors to the proper treatment of infections and infectious triggers of MCAS.
Low Histamine Diet
In our practice, we get the best results when a MCAS patient addresses their dietary triggers prior to incorporating any stabilizing medications or supplements. The diet helps to drive down the inflammation initially to allow the stabilizers to be more effective. If you would like more information from our in-office study, please see the full presentation under the “Media” tab.
If you want the cliff notes, we found that implementing diet before stabilizers brought down inflammation about 38% and stabilizers with diet only brought down inflammation 10%.
As my mentor put it so nicely -- If you are in the shower with the water running and you ask for a towel, you struggle to actually get dry. If you first turn off the water, you can effectively use the towel. The water is analogous to the environmental triggers that drive the inflammation including your diet.
Dietary intervention is the first essential step where one would eliminate:
High histamine foods
Avoid leftovers (easier than you think)
Avoid fermented foods like sauerkraut, kim-chi, yogurt and kombucha
Mast Cell Stabilizers
After several weeks of dietary management, one may add one or more of several mast cell stabilizers to help to continue to drive down the inflammation.
There are both natural and pharmaceutical interventions that can help to reduce histamine in the body.
Some examples of natural antihistamines include Quercetin, Holy Basil, Turmeric and probiotic strains that reduce histamine levels.
Some examples of pharmaceutical antihistamines include Benadryl (sedating), Claritin, Zyrtec, Ketotifen and Cromolyn Sodium.
Mast Cell Drivers
Though diet and mast cell stabilizers can manage MCAS symptoms, they still don’t address the driving force behind the condition.
As we continue to learn more, we are finding various factors drive this exaggerated immune response including:
Exposure to Water Damaged Buildings/Mold and Mycotoxins
Exposure and Sensitivity to EMFs
Emotional Stress and Trauma
Chronic infections including Parasites and Viruses
Environmental Toxins and Heavy Metals
In our treatment of Mold, Lyme and PANDAS/PANS patients, evaluation and treatment of MCAS has become a cornerstone for proper treatment. Once the inflammation has been contained, we are able to implement successful protocols with greater ease.


This breakdown of MCAS is so enlightening, especially since these symptoms can feel so overwhelming and unpredictable when you're right in the middle of a flare-up. I remember a particularly rough patch last spring where my brain fog and fatigue were so intense that I could barely look at a screen, let alone focus on my finals. I was in such a panic about my grades slipping that I actually caught myself wondering if I could find a way to have someone take my online exam for me just so I wouldn't fail while my body was crashing. It’s such a relief to find resources like this that validate the physical struggle of trying to keep up with academic and professional…
This post on Mast Cell Activation Syndrome is a great, concise explanation of how mast cells play such a critical role in our immune system. It really highlights how even essential cells can become problematic when overactive. Reading it made me think about situations where guidance is key, like needing someone to Do my biology class to fully understand all these mechanisms. Breaking complex topics into clear, real-world examples just like this article makes biology feel much more approachable.
Reading this post about What is Mast Cell Activation Syndrome (MCAS) helped me learn that MCAS is when your immune cells release too many chemicals and cause many strange symptoms, from itchy skin to belly pain and trouble breathing, even without a clear trigger. I once had a big school week and was so stressed that I leaned on service to do my assignment for me, and getting that help gave me time to read and understand things like this without feeling rushed. MCAS is a health condition where mast cells react too much, causing allergy‑like symptoms in different parts of the body, and managing it often needs care and medical support.
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