MCAS Symptoms: Headaches, Hives, Heartburn & More

By Amy Burkhart MD, RD

Mast cell activation syndrome, MCAS, is blamed for symptoms such as bloating, diarrhea, constipation, pain, headaches, rashes, fatigue, palpitations, and more. MCAS symptoms can be triggered by foods such as wine and cheese, but also by things such as exercise and stress. But, what exactly is MCAS? Is it real or another passing health trend?

Mast cells are part of our immune system

Mast cells are found everywhere in the body. Mast cells are front-line soldiers in our body’s immune response. They store and release important, natural chemicals that are part of the normal immune response. But, when over-activated or if there are too many mast cells, unwanted symptoms arise.

Mast cell disorders are a category of diseases, not one specific condition

All mast cell disorders have similar symptoms. MCAS is the only type of mast cell disorder with a normal number of mast cells. In all other forms of mast cell disorders, too many mast cells are produced. In both situations, symptoms occur.

In MCAS, the number of mast cells is normal but they are over-reactive.

All mast cell disorders except MCAS have specific diagnostic criteria. The understanding of MCAS is emerging. The specifics of how to diagnose it are not agreed upon but are being developed. (1).

MCAS is a rapidly developing topic, and research surrounding it is relatively recent.

Diagnosis is currently based on symptoms and the exclusion of other causes. Uniform testing protocols are not agreed upon.

People with MCAS do not have extra mast cells like other mast cell disorders. The number of mast cells is normal,  but they are overactive. MCAS diagnosis is made after the other mast cell disorders, and “look-alike” conditions are ruled out. Gene mutations are not seen in MCAS as in other mast cell disorders.

MCAS symptoms are different in everyone and range from mild to severe. Because mast cells act everywhere in the body, symptoms are different from person to person.

One study in Germany found 17% of the population had MCAS

Until there is a definitive and agreed-upon way to diagnose MCAS, the incidence will not be known.

We know that if you have a family member with MCAS, your chances of also having MCAS are higher. ((2) 3).

The starting point for MCAS testing depends on symptoms.

For example, an allergist or dermatologist may begin the evaluation if the symptoms are primarily rashes. If headaches are the issue, a primary care or neurology appt. may be made. With so many different starting points, you can understand the challenge of creating a uniform diagnostic path.

To have a confident diagnosis of MCAS, you must meet several criteria (4). Proposed diagnostic criteria were offered in 2010 (5).

1. Symptoms involve two or more organ systems (ex: skin and lungs)
2. Elevation of tryptase on a blood test, done during a flare or a positive urine for mast cell metabolites. Typically it is recommended these tests be done within 30 min-4 hours of symptoms
3. If these criteria are not met, someone may be called “ suspected MCAS” as long as other causes of the symptoms have been eliminated.
4. Certain conditions such as POTS syndrome and Hypermobile Ehler’s Danlos may co-exist with MCAS and be a clue to ‘Sub-types” of MCAS.

Getting a diagnosis of mast cell activation syndrome is made by the process of elimination, in addition to blood and urine testing, skin biopsy, and even bone marrow testing (rarely done but may be needed). Genetic testing may also be part of the path to diagnosis.

A process of elimination is not an unusual diagnostic path in medicine. Think of IBS or non-celiac gluten sensitivity. Diagnosis of these conditions is similarly based on symptoms and eliminating other conditions.

Conditions that can look like MCAS* must be considered “ruled out”:

• IBS- new research in 2021 shows mast cells are an important player in IBS (6,7)
• Autoimmune disorders
• Food/environmental allergies
• Undiagnosed celiac disease
• Eczema
• Multiple Chemical Sensitivity
• Fibromyalgia
• Chronic Fatigue Syndrome/Myalgic Encephalomyelitis
• Lyme disease
• Multiple sclerosis

*This list is not all-inclusive.

Stress, alcohol, and high histamine foods are common triggers.

• Other foods specific to an individual
• Strong scents
• Temperature changes
• Exercise
• Infection
• Medications
• Mold exposure
• Other environmental triggers such as warm environments

Difference between MCAS & Histamine Intolerance

MCAS may seem similar to histamine intolerance (HIT). Remember, there are several chemicals in mast cells; one of them is histamine. With MCAS, histamine plus other chemicals are released.

In histamine intolerance, the issue is too much histamine only.

Treatment involves medications, diet, and lifestyle changes.

For severe urgent/acute reactions, treatment must be immediate and is equal to treatment for an allergic reaction, and emergency care may be needed.

Medications:

Someone with MCAS should carry an epi-pen (prescription medication) at all times in case of emergency. Additional medications are both over the counter and prescription.

Antihistamines: These can be used topically and orally to manage symptoms.

• H1 Blockers: Allegra, Claritin
• H2 Blockers: Pepcid, Zantac

Mast Cell Stabilizers:

• Cromolyn:  This is a medication that may be helpful with managing long-term symptoms of MCAS. It should not be used to control an urgent situation.

Leukotriene Blockers

• Singulair

Monoclonal Antibodies

• Omalizumab: This may also help manage symptoms and prevent flares. It blocks the action of mast cells (8).

Steroids: These suppress the immune reaction and may be used to reduce swelling or help with breathing or rashes/itching.

• Prednisone or other similar steroids

Long-term treatment for MCAS requires a deeper dive to identify triggers. It is crucial to determine underlying “fixable” reasons for flares and provide tools for flare prevention.

Diets:

Dietary changes can be dramatically helpful for MCAS. However, at this time, there are few evidence-based diet intervention studies for MCAS. That does not deter people suffering from symptoms from trying diet changes to find relief. Many report success.

For this reason, I recommend anyone treating these patients to familiarize themself with what is being used by the lay public.

The following three diets are used most commonly for MCAS. A food log should be kept to assess which foods are problematic and which of the following diets may be the most beneficial.

None of these diet interventions are meant to be a long-term solution; however, variations of the diets may be long-term to keep symptoms at bay.

Working with a dietitian is recommended to avoid over-restriction, proper nutrition and decrease the possibility of developing food anxiety.

• Low Histamine Diet
• Low FODMAP Diet
• Elemental Diet

A low histamine diet is by far the most commonly used and best-studied and been shown to be helpful in asthma, non-responsive celiac disease, headaches, chronic urticaria/hives,  and mast cells/histamine implicated in IBS. A low FODMAP diet may be used if symptoms are primarily related to digestion/IBS, and the food diary shows these types of foods to be problematic. An elemental diet may be used in severe cases or in times of flares.

Additional  MCAS Treatment

• Supplements– Although none have yet been studied, patients often report improvement using supplements such as quercetin, fish oil, curcumin, DAO, and others. Specifics are beyond the scope of this article.
• Stress Reduction-Stress is a known trigger. Using a daily stress-reduction technique may prove helpful.
• Sleep-Good sleep helps everything!
• Exercise/Activity: Exercise can help or worsen symptoms. An individualized recommendation is often needed.
• Avoid triggers such as exposure to particular foods or environmental influences like heat or mold.
• Psychological support– Anxiety and Depression are common with any chronic health condition. Please assure to always address a person’s mental health.

Important things to remember about MCAS

1. MCAS is an emerging topic. It is different from other mast cell disorders. Make sure other mast cell disorders and health conditions are not the cause of the symptoms before settling on a diagnosis of MCAS.
2. Symptoms differ from person to person, but all symptoms in MCAS result from overactive mast cells.
3. The best way to diagnose it is still being researched. It is currently diagnosed after eliminating other possible causes of symptoms.
4. Identifying any underlying conditions that may affect mast cells, such as IBS, celiac disease, SIBO, IBD, or other autoimmune conditions is vitally important. Treating the underlying disorder will help the management and prevention of MCAS flares.
5.  Never give up on your health. Keep looking for answers until you find them.

Talk to your doctor

1. Many providers will not have heard of MCAS. Bring them published research, such as that listed below, to help legitimize your concerns.
2. Start with your primary care doctor, and they can refer you based on symptoms.
3. Allergists will be most familiar with mast cell disorders and may be a starting point for many.
4. If your provider doesn’t listen, search for someone familiar with mast cell disorders.
5. Don’t give up; you can get better.

• MCAS And Covid 2021
• Mast Cells And Food Intolerances 2021
• A Primer On Mast Cell Activation Syndrome For Gastroenterologists 2020
• Mast Cell Activation Syndrome: Proposed Diagnostic Criteria
• Familial Occurrence of Systemic Mast Cell Activation Disease
• Role Of Mast Cells In Autoimmunity
• Covid-19 Hyper Inflammation Related To Mast Cells

• American Academy Of Allergy And Immunology
• National Database Of Rare Diseases
• Mayo Mastocytosis Clinic
• NIH Mast Cell Disorders
• The Mast Cell Disease Society
• UK Mastocytosis Support Group