MCAS frequently asked questions

Histamine intolerance occurs when the body has impaired ability to break down histamine from foods, drinks, or certain medications. Although symptoms can overlap, MCAS cannot be managed or significantly improved through diet alone. ¹⁵

If you suspect one or both conditions, please speak to your general practitioner to establish whether a specialist referral is required.

Allergies involve the immune system reacting to a specific allergen, such as food, pollen, animals or medications. These reactions are usually IgE-mediated and follow a predictable pattern.

MCAS, on the other hand, involves inappropriate or excessive release of mast cell mediators in response to a wide variety of triggers, or sometimes without a clear trigger. In MCAS, the underlying issue is mast cell dysregulation rather than a defined allergic pathway.²⁵

Some patients with MCAS also have allergic conditions, referred to as secondary MCAS. In these cases, allergic reactions may contribute to episodes of mast cell activation, but the allergy is the primary condition and does not diagnose MCAS alone. Rather, it clarifies the subtype.²⁵

If you have confirmed or suspected MCAS and are concerned you also have allergies, please communicate this with your general practitioner when seeking a referral to a specialist. If you need a list of specialists in your state or territory, please contact us.

The “trifecta” is a term popularised by social media and used to describe the perceived co-occurrence of mast cell activation disorders (most often MCAS), Ehlers–Danlos syndrome (EDS), and postural orthostatic tachycardia syndrome (POTS).

Although some research suggests these conditions may appear together more often than expected, this has not been validated,¹⁰ and there is no confirmed evidence that they are connected by causation.^8,11 Likewise, none of these conditions diagnose or confirm the presence of the others.¹

This does not mean the conditions cannot co-occur. Many patients with MCADs report having two or more of these conditions, sometimes alongside others. However, it is critical to understand that there are no shared medical treatment pathways or guidelines established for dual or collective management of MCADs, EDS, and POTS.

While it is possible broad health improvements in any area may benefit someone’s overall health profile, in the first instance each condition must be assessed and managed by its own clinical specialist:

• MCADs are typically diagnosed by immunologists or haematologists
• EDS types are typically diagnosed by clinical geneticists or rheumatologists
• POTS is usually diagnosed by cardiologists

While some symptoms can overlap across these conditions, they may also indicate unrelated medical issues that require different or urgent or different interventions.¹² If you have a suspected or confirmed MCAD and believe you may also have cardiovascular or connective tissue symptoms, please speak to your general practitioner to establish the appropriate next steps for referral and investigation.

In cases where MCAS occurs alongside hereditary alpha tryptasemia (HαT), it is important to note that HαT is an autosomal dominant trait, meaning there is a 50 per cent chance of passing it to a child if one parent carries the trait. However, HαT is a genetic trait and not a diagnostic criterion for MCAS. Additionally, many individuals with HαT, with or without MCAS, are not symptomatic.^{3, 4}

If you have HαT and require support to understand the implications for any current or intended offspring, please speak with your general practitioner or specialist for further guidance.

Some patients with MCAS report increased sensitivity to triggers during pregnancy, while others experience improved stability. If you are pregnant or planning a pregnancy and have confirmed or suspected MCAS, please speak with your general practitioner or specialist for guidance that may apply to your individual management needs.^26,27,28

General practitioners (GPs) and allied health practitioners can play an important role in recognising early immunological symptoms, supporting referrals and helping coordinate care after a diagnosis is achieved. However, suspected MCAS should always be assessed and confirmed by an immunologist, occasionally alongside a haematologist.

Validating a suspected MCAS diagnosis with a specialist is important as all recognised subtypes of MCAS have specific criteria and are generally diagnoses of exclusion, meaning other conditions with similar symptoms need to be ruled out first. A formal specialist diagnosis confirming your MCAS subtype can help guide treatment planning, trial eligibility and management of coexisting conditions. Proper documentation can also be important in emergency care, where unofficial diagnoses may not be considered sufficient to guide treatment.

While specialists, particularly private specialists, can be costly, it should be viewed as a critical part of diagnosing and managing MCAS. After this period, some patients may only require specialist reviews every 6-12 months, with day-to-day care continuing under their GP or allied health practitioner.

If you have been told you may have MCAS, you can contact us with your state (and for children, age) to receive a list of practitioners.

Note: For more information about medical costs, you can refer to the Medical Costs Finder, an Australian Government website that helps patients understand typical costs for common private health treatments, compare prices across locations and prepare for medical expenses.

If you have MCAS and are concerned about your diagnosis, or if your symptoms change significantly over time, please speak with your general practitioner or specialist to determine whether further assessment or updated testing is appropriate.

Treatment focuses on reducing mast cell mediator release, managing symptoms and identifying triggers where possible. Many patients experience improvement with appropriate medical support, medication trials and lifestyle adjustments, while others may continue to have fluctuating symptoms over time. However, with appropriate care, most patients can achieve meaningful improvements in stability and quality of life.

If you have confirmed or suspected MCAS with symptoms impacting your daily activities and quality of life, please speak with your general practitioner or specialist for further guidance.

Excipients are inactive ingredients used to stabilise, preserve or deliver medications. Many are very safe and widely used, including in everyday food products.¹³

While some patients with MCAS may be sensitive to specific excipients such as dyes, preservatives, alcohols, gels or particular filler ingredients, having MCAS does not require you to avoid excipients in general. Reactions are individual, not universal, and avoiding all excipients unnecessarily can make treatment access difficult and may limit safe medication options.¹⁴

If you believe you have reacted to a medication, it is important to work with your general practitioner or specialist so they can help determine whether the reaction was caused by the medication itself, a specific excipient or unrelated mast cell reactivity.

If an excipient is considered the likely issue and commercially available alternatives are not suitable, you may be recommended to work with a compounding chemist. Compounding pharmacies can assist by trialling different binders, fillers, bases or capsule types that do not contain the suspected ingredient.

TAMS has compiled a list of compounding pharmacies in Australia and Aotearoa New Zealand.

There is currently no validated literature or broad population evidence demonstrating that GLP-1 medications, cannabis products or low-dose naltrexone address symptoms that arise directly from mast cell activation. None of these therapies is an established or recognised treatment for any mast cell activation disorder, but rather have other specific indications.

While these medications and products are frequently promoted online as having various benefits, and may be increasingly easy to access, please do not start GLP-1s, cannabis, LDN or any other therapies suggested online for management of mast-cell mediated symptoms directly or otherwise without discussing their relevance to your diagnosis and overall health with your specialist. 

Your GP or specialist will determine whether any of these treatments are appropriate, safe and compatible with your individual medical needs.

Access depends on the medication. Some medicines may be available through compounded pharmacies, while others may only be accessible through the Personal Importation Scheme or the Special Access Scheme.

Please speak to your specialist, as they are best placed to advise you on suitable access pathways in the first instance. However, if they are unfamiliar with the available options, TAMS may be able to help. You or your specialist are welcome to email us noting the name of the medication, and we will provide any useful information available to us. Please kindly do not include dosage details in your message.

It’s not contagious or inherited, but in adult cases it is chronic, and requires life-long management. With good medical care and support from their community, many MCAS patients can manage their symptoms and participate fully in school, work and daily life.

Read more about MCAS.

Note: When living with MCAS, letting others know about your triggers, what to do in an emergency, and any medications (like an EpiPen/AnaPen) you carry, can help them support you. In addition to TAMS’ 2025 brochure, which provides an introductory overview of mast cell activation disorders, including mastocytosis, you may also find our MCAD resources page helpful. This page includes educational webinars, infographics and information sheets, along with other written resources that may assist in communicating your or your child’s diagnosis with schools, employers and family members.

Many patients with mast cell activation syndrome can travel safely with preparation. It’s important to carry your medications, emergency action plan and any autoinjectors with you at all times. Patients should also travel with a medical letter, especially when flying or travelling overseas.

For more information on what information should be in a medical letter please visit the Department of Health, Disability and Ageing – Office of Drug Control or New Zealand Customs Service – Te Mana Ārai o Aotearoa.

Some patients may try low-histamine or low-FODMAP diets under medical supervision, but there is no evidence of their benefits for MCAS in general. Long-term restrictive diets without cause significant risks, including for nutritional deficiencies.¹⁷

If you find that certain foods trigger their symptoms, such as flushing, stomach upset, or fatigue this may be a secondary health issue such as histamine intolerance. Please always discuss any food reactions with your doctor to ensure allergies and other conditions such as celiac are ruled out.

To find a dietician who can help you with managing any confirmed food issues, or to generally improve your nutrition, head to the look up tools on Dietitians Australia or Dietitians NZ.

If exercise has triggered symptoms before, talk to your specialist about how to exercise safely.

Some patients with MCAS who are sensitive to stimuli may experience symptoms such as flushing, rash or short-lived increases in baseline reactivity after a vaccine, but these are usually mild and self-limiting. However, individuals with a history of adverse vaccine reactions, particularly anaphylaxis, should speak to their specialist about how to safely plan for upcoming vaccines.^18,19,20

There is no validated or large-population evidence that medically necessitated or cosmetic implants (including contraceptive devices, joint implants, dental implants, mesh or cosmetic fillers) cause MCAS or lead to its development. MCAS is not known to be triggered by a single exposure or implanted material.^8,21

Some small studies have observed increased mast cells or inflammation in tissue surrounding breast implants, particularly in people who already report symptoms, which may suggest that mast cells may be involved in local inflammatory or immune responses.²² However this does not equate to evidence that implants cause MCAS or that having an implant leads to the condition developing.

While some MCAS patients may experience sensitivity to components such as adhesives, metals, dyes or local inflammation around an implant these reactions are generally related to mast cell reactivity rather than the implant itself causing or worsening MCAS. In most cases, symptoms are temporary and can be managed with standard supportive medications and coordination with the treating specialist.^23,24

If you have MCAS or are being assessed for it, and have a history of reacting to medical equipment or materials such as metals, contrast dyes, latex or certain adhesives, it is important to inform your specialist, surgeon, dentist or procedural team before any procedure, including consideration of an implant, so the safest approach can be planned for you.

Your managing surgeon and procedural team are best positioned to guide your pre- and post-operative care. Where necessary, your immunologist may also offer additional advice or coordinate with your other specialists. You may also request a letter from your immunologist outlining important considerations for your care.

Currently, there are no well-validated guidelines for pre- and post-procedural management, as triggers and clinical needs vary between patients and MCAS subtypes. Planning should be tailored to your known triggers, previous reactions, current treatment, and clinical needs.

However, since both MCAS and mastocytosis can involve mast cell activation during medical, dental, and surgical procedures, the following resources may help guide discussions with your care team:    

• The Mast Cell Disease Society – Perioperative Management for Patients with Mast Cell Diseases
• Royal College of Anaesthetists – Mastocytosis and Anaesthesia: Advice for Patients
• OrphanAnesthesia – Systemic Mastocytosis
• Mastocytosis-MCAS – Navigating Medical and Dental Procedures

Eligibility for the Disability Support Pension (DSP) depends on the functional impact of the condition, the level of impairment, and whether it affects an individual’s ability to work 15 hours or more per week on an ongoing basis.

Other Centrelink programs, such as JobSeeker payment, have different eligibility requirements and may offer temporary medical exemptions of up to 24 months where an individual is unable to work or meet mutual obligation requirements due to illness or disability.

DSP inquiries should be raised directly with treating specialists, general practitioners or, for general inquiries, Services Australia.

You may also wish to contact a national or local disability advocacy organisation for further guidance or support.