MCAS treatment

Managing MCAS is often complex due to its variable presentation and fluctuating severity. Challenges also remain, as the validated diagnostic criteria have not yet been formally adopted universally.^6,17,21 Despite this, many patients achieve meaningful symptom reduction and improved quality of life through a personalised combination of symptom tracking and trigger avoidance, other lifestyle adjustments and use of medication.¹⁰

As MCAS encompasses several subtypes, including secondary MCAS, it is important to understand that while much medical management applies across all types, approaches are not always linear. For some patients who meet criteria for secondary MCAS or who have confirmed food allergies, targeted food exclusion may be required. Broadly, however, dietary adjustments are not a treatment for MCAS. In most cases, any adverse reactions attributed to MCAS prove to be food intolerances rather than true food allergies, or may relate to comorbid conditions such as Irritable Bowel Syndrome.^22,23

In those who have suspected allergies, intolerances or a diagnosis of secondary MCAS, identifying true food intolerances through a medically structured elimination and reintroduction process is a short-term, physician or dietitian-led approach. It is not recommended under any circumstances for patient-led assessment. When required, these changes should be guided either by treating specialists or experienced dietitians, and care should be taken to avoid unnecessarily prolonged or overly restrictive diets, as these can lead to nutritional deficiencies.²

Note: While low-histamine or low-FODMAP diets are often promoted online as offering general benefit for MCAS, evidence supporting their effectiveness remains extremely limited and is not validated. Please do not start diets advertised for managing illness without consulting your general practitioner or specialist.

Medications

MCAS is a complex condition and requires clinical oversight for all forms of treatment, including over-the-counter medications. Management typically focuses on reducing mast cell mediator release and, when possible, identifying and avoiding triggers. While many patients can manage symptoms with antihistamines and other low-impact supportive therapies, treatment should always be personalised and guided by a specialist.

Note: If a general practitioner or another non-specialist suspects an MCAS diagnosis for yourself or your child, referral to a treating specialist is essential to confirm the diagnosis and establish appropriate treatment planning, medication trials, and titration.

If you or your child do not currently have a diagnosis or treating specialist, please contact us for a list applicable to your state or territory.

Paediatric management

Evidence for paediatric MCAS remains limited, and published data on children meeting validated diagnostic criteria are rare. However, in children with symptoms that strongly suggest mast cell activation, where validated testing supports activation, and other causes have been carefully excluded, management is tailored to symptoms and generally begins with generally low-risk medications used in other allergic or mast cell–mediated conditions.³

For example, non-sedating or sedating H1-antihistamines may help manage skin or general allergic-type symptoms. Gastrointestinal symptoms may, depending on age and at the discretion of their specialist, receive support from H2-antihistamines, proton pump inhibitors (for short periods) or mast cell stabilisers such as sodium cromoglycate.²⁴

Note: While some medications are available over the counter, including age-specific formulations, paediatric management must be directed by a specialist. This is particularly important in children because there is limited paediatric cohort data and no long-term safety data on the use of these adjunct therapies in children diagnosed only with MCAS. Please always seek guidance from your child’s specialist before starting any medications to establish monitoring needs and ensure safety and well-being.

Adult management

Medication needs in adults with MCAS vary significantly and are influenced by the patient’s subtype, symptom pattern and any co-existing conditions. These may include allergic disease, gastrointestinal disorders or cardiovascular issues or other conditions, all of which require their own distinct medical management and should not be treated as part of MCAS itself. Once these factors are understood, treatment focuses on reducing mast cell mediator release and addressing specific symptom clusters, often through a combination of antihistamines, stabilisers and other supportive therapies tailored to the individual.

Common medications

• H1-antihistamines (e.g. cetirizine, desloratadine, fexofenadine): May help reduce itching, flushing and allergic-type symptoms.^6,15,24
• H2-antihistamines (e.g. famotidine, cimetidine): May assist with gastrointestinal symptoms such as reflux or abdominal pain.^6,15,24
• Mast cell stabilisers (sodium cromoglycate): May help reduce mast cell degranulation and assist with gastrointestinal or systemic symptoms.^6,24,25
• Ketotifen (H1 antihistamine with mast cell–stabilising properties): May assist with symptoms such as itching, ocular irritation, flushing and other mast cell–related symptoms that may occur during flares.^6,21,24
• Leukotriene receptor antagonists (e.g. montelukast): May assist with airway reactivity, flushing and inflammation.^6,15,24
• Proton pump inhibitors (e.g. omeprazole, esomeprazole): Useful for acid reflux and some forms of gastritis in cases of suspected or confirmed mast-cell involvement. Ongoing use should always be guided by specialists.¹
• Topical corticosteroids: May be used for localised skin inflammation or irritation.^15,24
• Oral corticosteroids: Reserved for short-term use in severe flares, and should always be used under specialist guidance.^6,15
• Non-steroidal anti-inflammatory drugs (e.g. aspirin): May be used to address prostaglandin-related symptoms such as flushing, bone pain, or brain fog.^6,21,15,25 However, use of this medication class must only be informed by a specialist as MCAS patients can carry an increased risk of adversity or side effects.²⁶
• Monoclonal antibodies (e.g. omalizumab/Xolair): May help reduce the frequency and severity of reactions, particularly in patients with recurrent anaphylaxis or multisystem reactivity not controlled by standard therapies, although this is not an MCAS-specific treatment.^6,15
• Epinephrine auto-injectors (e.g. EpiPen, Anapen): Prescribed when there is a risk of anaphylaxis or severe systemic reactions.^15,24

Note on venom allergy and venom immunotherapy in MCAS

Unlike mastocytosis, venom immunotherapy (VIT) is not routinely indicated for MCAS. However, if a patient with monoclonal MCAS (MMAS) also has confirmed IgE-mediated venom allergy, their specialist may recommend VIT in line with standard allergy guidelines.²⁷

If you have a venom allergy and MMAS please speak to your specialist to understand if VIT is appropriate in your case.