What Triggers Mast Cell Activation Syndrome? A Functional Medicine Perspective On What Could Be Flaring Up This Condition

In my telehealth functional medicine clinic, I often see people who are dealing with unexplained symptoms related to complex mast cell disorders like mast cell activation syndrome. Itching, racing heart, brain fog, shortness of breath, and digestive distress are all symptoms that can come on suddenly, almost like an allergic reaction, but without any known allergen present. This can be frustrating for people living with this condition, not only because they feel like they are living in a perpetual allergy season, but because they don’t know what is causing their symptoms.

So what triggers mast cell activation syndrome? While triggers can vary significantly from person to person, there are several well-known triggers (such as medications, foods, and stress) that can cause this condition to flare up. Read on to learn more about mast cell activation syndrome and a comprehensive list of the most common MCAS triggers so you can start your journey toward healing.

What is mast cell activation syndrome (MCAS)?

Mast cell activation syndrome (MCAS) is a condition where the mast cells in your body mistakenly release excessive amounts of chemicals known as mast cell mediators.

In a healthy individual, mast cells — a type of white blood cell — are only triggered when you encounter an allergen. However, in the case of mast cell activation syndrome, these mast cells release mediators even when there’s no allergen present. 

Everything from stress to exercise can trigger MCAS but the release of mediators can also be spontaneous. This makes it extremely difficult for people with MCAS to move through daily life, not only because they feel like they are living in a perpetual allergy season, but because they don’t know what is causing their symptoms.

Symptoms of mast cell activation syndrome

Because symptoms of mast cell activation syndrome look so similar to allergies, it can often take a while for people to get diagnosed. Symptoms can vary widely between individuals, but in general, they typically fit into 4 main categories: skin, gastrointestinal, cardiovascular, and respiratory.

• Skin: Rash, itching, chronic hives (urticaria), flushing, swelling (angioedema), sweating
• Gastrointestinal: Nausea, vomiting, diarrhea, abdominal cramping, abdominal pain
• Cardiovascular: Low blood pressure (hypotension), rapid heart rate (tachycardia), lightheadedness, fainting (syncope), exercise intolerance (1, 2)
• Respiratory: Trouble breathing, runny nose, wheezing

In most people, two body systems or organs are affected at the same time. Symptoms can also take on a neurological component, adding another layer to diagnosis. That can look like brain fog, fatigue, headaches, anxiety, and an increased risk of mood disorders. (3)

What triggers mast cell activation syndrome?

There are 3 main types of MCAS: primary, secondary, and idiopathic MCAS. (4) Primary MCAS involves cell mutations (like in the case of mastocytosis) that lead to an abnormal growth of mast cells and secondary MCAS happens when mast cells are activated due to another condition like Ehlers-Danlos syndrome, POTS, or from an IgE-dependent allergy, like peanuts or pet dander for example. Idiopathic MCAS has no obvious cause.

While researchers understand that idiopathic MCAS involves your immune system, similarly to autoimmune disease, everyone’s biochemistry is unique and there are many possible factors (or culmination of factors) that can lead to the development of this condition.

With this being said, regardless of the exact cause of MCAS, there are also many possible triggers to MCAS symptoms. Although the symptoms of this condition can mimic an allergic reaction, we know that MCAS is a lot more complex, and not everyone is going to be triggered by the same things. There are, however, a handful of things that have been known to cause reactions most often in those with MCAS.

1. Certain Foods

The biggest, most frequently suspected trigger for MCAS is food. This is because there are a lot of “healthy” foods that naturally contain histamine or trigger the release of histamines in the body — which are also released in MCAS. 

It’s possible to have both histamine intolerance and MCAS, but if you have MCAS, these foods can still exacerbate MCAS symptoms even if you take antihistamines or don’t have histamine intolerance:

• Aged cheeses
• Alcohol
• Avocados
• Bananas
• Canned, smoked, cured, or pickled foods
• Chocolate
• Eggplant
• Fermented foods (sauerkraut, kimchi, and kefir)
• Legumes (soybeans, chickpeas, and peanuts)
• Licorice
• Mushrooms
• Processed food
• Some nuts (almonds and pistachios)
• Some seafood (shellfish, sardines, and tuna)
• Soy products (soy sauce and tofu)
• Spinach
• Strawberries
• Tea
• Tomatoes and tomato-based products
• Tropical or citrus fruits (kiwi, lemon, lime, papayas, and pineapple)
• Vinegar

Keeping a food and symptoms journal is a great way to help narrow down what foods, if any, trigger your symptoms.

READ MORE: How To Follow A Low Histamine Diet (And Is It Right For You?)

2. Alcohol

Alcohol isn’t the healthiest for many reasons (it’s inflammatory by nature) but for those with mast cell activation syndrome it can be particularly problematic. Not only can alcohol itself trigger a release of mast cells, alcohol can actually block diamine oxidase (DAO), an enzyme responsible for helping your body clear out excess histamine.

3. Stress

Stress is one of the biggest triggers for chronic health problems I see in my telehealth functional medicine clinic. This is because your nervous system and immune system are deeply connected. In fact, stress can act like a gas pedal for mast cells.

Studies have found that stress can essentially communicate directly with mast cells through molecules like CRH, telling these immune cells to become more active. (5) When mast cells respond, they release inflammatory compounds that can worsen symptoms and contribute to a cycle of stress and inflammation.

4. Temperature changes

Temperature changes are one of the most commonly reported triggers in individuals with mast cell activation syndrome. For people with MCAS, hot showers, saunas, and even summertime temperatures can lead to itching, dizziness, and other uncomfortable symptoms that make participating in certain activities almost unbearable. 

Cold temperatures can also trigger MCAS symptoms but not as often as heat. Researchers have identified three tiers of temperature response with high responders experiencing severe symptoms from both heat and cold, intermediate responders experiencing symptoms only to heat, and low responders that experience minimal, if any, symptoms to heat or cold. (6)

5. Exercise

Not only can the temperature change due to physical activity trigger symptoms, but exercise itself can be another trigger — as well as a potential healing tool. A recent study published in the Journal of Education, Health and Sport found that there was a bi-directional relationship between MCAS and exercise with it acting as both a trigger for severe reactions like anaphylaxis and a potential therapeutic tool for this condition. (7) This is another reason why it is so important to work with a qualified practitioner to determine the best healing plan for your particular case.

6. Infections

Getting sick can place a lot of stress on your immune system and can trigger mast cell symptoms. Whether that is from a viral, bacterial, or fungal infection, or the medication used to treat the infection, people with MCAS can oftentimes feel worse when their symptoms overlap with whatever infection they are trying to fight off.

8. Environmental toxins

The things you breathe in can also be a trigger for MCAS. Some of it may seem obvious but others can hide away in plain sight. Perfumes, cleaning supplies, and smoke are all potential triggers that are easier to identify. But more insidious toxins like mold and other pollutants in the air can be both harder to pinpoint and more difficult to eradicate, making toxin and mold testing even more important when determining if someone is dealing with MCAS.

Understanding MCAS triggers

The most confusing and frustrating aspect of MCAS is how to navigate your triggers — especially if you don’t know what they are or if they change. Yes, symptoms don’t always stay the same. You might tolerate a certain food for a while and then suddenly start noticing symptoms. This is known as a “threshold”. 

Everyone has a different threshold of what their body can and cannot tolerate, and it ebbs and flows over time. For example, you might be able to tolerate a food one day but react after eating that same food while you are fighting an infection or after you were exposed to extreme temperature changes. Each one of those factors contributed to the overall burden on your system. Add another potential trigger to your system, and it goes haywire. Think of it like this: you already filled your cup to the very top with water and tried to add more, causing it to spill over the edge.

But this is also good news! As you continue on your healing journey your overall burden starts to lighten. It’s like taking slow sips from that same cup until you have enough room to add a little more water.

LISTEN: Food Sensitivities, Mast Cell Histamine Hacks, Hydrogen Water, EMDR + Natural Flavors | Ask Me Anything

How to diagnose MCAS

There is no specific test, such as a single blood panel or tissue biopsy, to diagnose this MCAS. You can run labs that look at levels of mast cell mediators like tryptase and their metabolites; however, these tests are the most accurate when you are in an active symptom flare. 

But just because you have symptoms that resemble mast cell activation syndrome doesn’t mean you have MCAS. Remember, symptoms of MCAS overlap with a variety of health problems including allergies, autoimmune conditions, gut dysfunction, and other similar conditions like histamine intolerance. A good rule of thumb is to take note of whether or not your symptoms involve two or more of the four organ systems.

SHOP: Depending on your specific case, a targeted supplement designed to alleviate symptoms of excess histamine can be beneficial. Since I’ve seen this so much in my telehealth functional medicine clinic, I developed Hist Guard™,  a patented enzyme formula containing diamine oxidase (DAO)—the main enzyme responsible for the degradation of ingested histamine. This enzyme has been clinically tested and found to break down food-derived histamine in the digestive tract. DAO is not absorbed and does not have systemic activity. If you are not sure if this is right for you, talk with your doctor as Hist Guard does not manage or address antibody-related or IgE-related food allergies.

The Takeway

There’s no doubt that mast cell activation syndrome can be difficult to navigate. But there is so much hope for healing with the right plan and healing tools. Keeping a record of your symptoms and when they occur will help you better identify your individual triggers. Knowing what flares up your symptoms empowers you with the knowledge you need to move through daily like while in the midst of your healing journey. 

In my telehealth functional medicine clinic, we run multiple labs to assess for underlying gut dysfunctions, mold toxicity, hormone imbalances, and more, alongside a comprehensive health history to determine the root cause behind your symptoms. Once we have a clearer picture of the underlying mechanisms behind your MCAS diagnosis, we can then tailor a plan to help you reclaim your health.

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe. 

Photo: Unsplash.com

Sources

• Kohno, R., Cannom, D. S., Olshansky, B., Xi, S. C., Krishnappa, D., Adkisson, W. O., Norby, F. L., Fedorowski, A., & Benditt, D. G. (2021). Mast Cell Activation Disorder and Postural Orthostatic Tachycardia Syndrome: A Clinical Association. Journal of the American Heart Association, 10(17), e021002. https://doi.org/10.1161/JAHA.121.021002
• Luttrell, M. J., & Halliwill, J. R. (2017). The Intriguing Role of Histamine in Exercise Responses. Exercise and sport sciences reviews, 45(1), 16–23. https://doi.org/10.1249/JES.0000000000000093
• Weinstock, L. B., Nelson, R. M., & Blitshteyn, S. (2023). Neuropsychiatric Manifestations of Mast Cell Activation Syndrome and Response to Mast-Cell-Directed Treatment: A Case Series. Journal of personalized medicine, 13(11), 1562. https://doi.org/10.3390/jpm13111562
• The Mast Cell Disease Society, Inc. (n.d.). Mast cell activation syndromes. https://tmsforacure.org/overview/mast-cell-activation-syndromes/
• Theoharides, T. C. (2020). The impact of psychological stress on mast cells. Annals of Allergy, Asthma & Immunology, 125(4), 388–392. https://doi.org/10.1016/j.anai.2020.07.007
• Häder, T., Molderings, G. J., Klawonn, F., Conrad, R., Mücke, M., & Sellin, J. (2023). Cluster-Analytic Identification of Clinically Meaningful Subtypes in MCAS: The Relevance of Heat and Cold. Digestive diseases and sciences, 68(8), 3400–3412. https://doi.org/10.1007/s10620-023-07921-5
• Kierska, A. E., Polak, M. B., Płóciennik, J., Kania-Bonicka, Z. M., & Łuczyńska, G. E. (2026). Physical exercise as a trigger and therapeutic tool in mast cell activation syndrome: A narrative literature review of mechanisms and management strategies. Journal of Education, Health and Sport, 93, 72700. https://doi.org/10.12775/JEHS.2026.93.72700