Mast cells play an important role in immunity, as they release substances that can trigger the immune system. Mast cell activation syndrome (MCAS) is a condition that causes mast cells to release these substances too frequently and often, resulting in severe allergic reactions.
After detecting an allergen, mast cells are responsible for releasing substances called mediators. This results in inflammation, which is the same response that occurs during an allergic reaction, and helps the body heal.
In people with MCAS, however, mast cells are overactive and cause severe allergic reactions.
This article will discuss MCAS’s causes, risk factors, symptoms, and diagnosis. It will also explore how MCAS differs from mastocytosis, some treatments and remedies, and tips for managing MCAS at home.
When foreign bodies are present, mast cells respond by releasing stored substances, called mediators, from their granules in a process known as degranulation.
These mediators, which include chemicals such as histamine, cause an inflammatory cascade. This results in the recruitment of white blood cells, swelling, smooth muscle constriction, and increased mucus production to destroy the allergen.
In people with MCAS, the immune system inappropriately activates mast cells, causing them to release too many mediators. This results in a person experiencing severe allergic reactions that affect several body systems repeatedly.
There are currently no data on the prevalence of MCAS. This is probably due to its wide range of clinical presentations, which makes it difficult for doctors to identify and confirm its diagnosis.
One 2016 study suggests that MCAS develops due to mutations in the transmembrane tyrosine kinase (KIT) gene, which is a regulator of mast cells. Similarly, an
Although many people cannot identify a trigger for the onset of their MCAS symptoms, most people report exposure to some stimuli. Some potential triggers include:
- sudden temperature changes
- certain foods and beverages
- alcohol, drugs, excipients, and vaccines
- venoms, such as those from snakes, jellyfish, spiders, and insects
- physical, emotional, and environmental stress
- contrast dyes
- surgical, dental, invasive, and radiological procedures
- hormonal fluctuations
- touch, friction, mechanical irritation, and vibration
A person’s symptoms may develop abruptly and irregularly, or they may occur frequently and persistently.
In MCAS, triggers induce a spontaneous release of mediators that can affect multiple systems. Some symptoms that people might experience in different parts of the body include:
A person may receive a diagnosis of MCAS when they present with both clinical symptoms and a laboratory profile indicative of the condition and when a doctor excludes other conditions.
Based on a consensus from the American Academy of Allergy, Asthma & Immunology, a person should meet the following criteria to receive a diagnosis of MCAS:
- They should have recurrent episodes of severe allergic reactions (anaphylaxis) present throughout the body, involving at least two of the following bodily systems:
- the heart
- the skin
- the lungs
- the gastrointestinal tract
- Their symptoms need to be associated with an increase in specific biologic mast cell mediator levels in the blood or urine. Biomarkers include histamine, tryptase, PDG2 and its metabolites, and LTC4 and its metabolites.
- There should be a reduction in the mediator levels and a complete resolution of symptoms after receiving medications (anti-mast cell mediator therapy) aimed at the increased mediator.
Although both conditions are diseases of mast cells and present with similar symptoms, they are different.
Mastocytosis occurs when a gene mutation causes the body to produce too many mast cells. MCAS is an activation disorder, which means that a person has an average amount of mast cells but frequently releases an excessive amount of mediators, causing a severe reaction.
If the person meets the criteria for a diagnosis of MCAS, it is important for a doctor to rule out a primary clonal mast cell disorder as the cause.
This requires further blood testing for a mutation called KIT D816V and, depending on those results, may require a bone marrow biopsy. If the bone marrow biopsy is negative, the diagnosis will be “idiopathic” MCAS.
Currently, there is no cure for MCAS. However, its management is similar to anaphylaxis management. Doctors can also provide symptomatic treatment based on an individual’s presentations.
Treatment will typically start with a quick administration of epinephrine, provision of oxygen, and IV antihistamines. Doctors may also provide a person with auto-injectable epinephrine in case of emergencies. People with chronic MCAS may need corticosteroids.
Depending on the person’s symptoms, a doctor may give them one or a combination of the following medications for allergic reactions:
- first generation H1 blockers, such as diphenhydramine
- second generation H1 receptor blockers, such as cetirizine
- H2 blockers, such as ranitidine
- leukotriene inhibitors, such as montelukast
- monoclonal antibodies, such as omalizumab
- mast cell stabilizers
Because stress is also a trigger for mast cell activation in MCAS, a person may also wish to consult with a therapist or learn relaxation techniques and exercises to help manage their stress.
Aside from taking medications, people with MCAS should try to avoid exposure to any trigger that may activate their symptoms.
Some tips and home remedies to help manage MCAS include:
- Opting for more natural solutions: Many household, hygiene, and beauty products contain toxins and chemicals. A person can reduce their exposure to these toxins by opting for more natural options.
- Avoiding foods high in histamine: A person should try to avoid histamine-rich foods, such as fermented products, cured and canned meats, preservatives, tomatoes, alcohol, citrus, and chocolate. Learn more about low histamine diets here.
- Immediately treating any infections: Infections can trigger mast cells. People should test for pathogens and treat them promptly to ensure that the body does not go through an inflammatory response.
- Avoiding other triggers: People should attempt to avoid possible triggers — such as sudden changes in temperature, insect bites, exposure to chemicals, and mechanical irritation — as often as they can.
- Improving gut health: One 2019 study suggests that MCAS symptoms overlap with functional gastrointestinal disorders. People may benefit from improving their gut health by avoiding foods that can cause gut inflammation and damage.
MCAS occurs when mast cells frequently release an excessive amount of mediators in response to triggers. This causes people to experience severe reactions.
There have been few studies on MCAS due to limited awareness and diagnosis of the condition.
People with MCAS have varying symptom presentations and frequencies. Although there is currently no cure for the condition, there are several treatment options that can help manage its symptoms.