Paediatric mast cell activation syndrome overview

Paediatric mast cell activation syndrome overview

Mast cell activation syndrome (MCAS) refers to a diverse group of disorders causing recurrent symptoms across multiple systems due to mast cell mediator release.^1,2 It is a condition where mast cells are present in normal numbers but become excessively and inappropriately activated. When activated, these cells release chemical mediators that may cause symptoms across multiple body systems. These symptoms can include itching, rashes, flushing, gastrointestinal pain or diarrhoea, fatigue, cardiovascular issues such as light-headedness, and, in some cases, allergic reactions or anaphylaxis.¹

MCAS is not contagious, does not cause an immune deficiency (though may exist with it), and does not make a child immunocompromised.² It also does not cause developmental or cognitive impairment. With support from trusted adults to avoid triggers, manage symptoms and take any required medication, most children can attend school, childcare and extracurricular activities just like their peers. 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.

MCAS is predominantly documented in adults, with the clinically preferred criteria for MCAS rarely fulfilled in paediatric cases. When mast cell activation is identified in children, it is most often a secondary outcome of IgE-mediated allergic mechanisms (secondary MCAS).³ While other documented paediatric cases exist, the challenges in verifying diagnostic pathological findings, along with complexity of symptom presentation, often leads to delayed diagnosis.⁴

Symptoms

MCAS can affect multiple organs, resulting in a wide range of symptoms including:⁴

• Skin – facial flushing, itching and hives.^1,5
• Gastrointestinal – abdominal pain, cramping, diarrhoea, nausea and vomiting.^1,5
• Respiratory – wheezing, chest tightness.¹
• Nasocular – pruritus, nasal stuffiness, conjunctival injection.¹
• Cardiovascular – hypotension, tachycardia, chest pain/tightness.^1,5
• Brain – headache, lightheadedness, brain fog*.^5,6
• Systemic – fatigue, anaphylaxis.^1,5

*Acute episodes of mast cell mediator release and activation may cause transient cognitive impairment when accompanied by hypotension or other significant mediator effects. However, chronic or persistent brain fog is not established to be a direct consequence of excessive mast cell activation, and alternative causes should be investigated.

Identifying triggers

Determining and managing triggers in MCAS is often complex and typically involves a process of trial and error. There is no single list of foods, hormones, environmental exposures, or lifestyle factors that will cause symptoms in all patients with MCAS.^2,7,8 Triggers and their severity can vary widely, even among patients within the same subtype.

As social awareness of MCAS increases, an influx of information is being shared online including about trigger identification and management. Some sources, including those published by healthcare professionals, promote extensive lists of potential triggers as if they are universally applicable or inherently beneficial. This is incorrect, and non-discerning implementation of such advice is often harmful and provides no benefit.⁹

In the absence of a confirmed history of anaphylaxis, avoiding potential triggers such as entire food groups, physical activity, or common environmental exposures such as sun, may not improve outcomes and can negatively affect overall health and quality of life.¹⁰

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.⁴

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.¹¹

Supportive care

While confirmed cases of MCAS are rare in children, documented instances do exist. Supportive care for paediatric MCAS typically includes treatments with common medications to control generally mild symptoms, such as itch or gastrointestinal issues. However, as Secondary MCAS is the most prevalently documented paediatric subtype, often occurring as a response to underlying allergic or inflammatory conditions, some children may require adrenaline autoinjectors and dietary adjustments in addition to standard medications.^4,12

For children who carry adrenaline autoinjectors, supportive care should include age-appropriate education on their safe use, as well as clear language to seek help from adults during an emergency.¹³ Families and school staff should know how to recognise symptoms of anaphylaxis and respond effectively.¹³ Empowering children with a sense of confidence and understanding around their condition can help reduce anxiety and improve overall safety.

Pre-teens and adolescents, particularly those with known allergens, should also receive formalised education on drug and alcohol safety to reduce the risk of severe reactions. This includes understanding potential cross-reactivity, the dangers of unmonitored substances, and recognising symptoms of an allergic or mast cell-related reaction. More information on these issues can be found at Allergy250k YA.

Supportive care throughout school, activity and care environments

As mast cell activation syndrome (MCAS) is considered rare in children, the diagnostic process for the condition, or diagnoses with similarly occurring symptoms, is often drawn out. It is important that children who are displaying symptoms, as well as those with confirmed diagnoses, receive support across care, school and activity settings.

Even in the absence of a confirmed diagnosis, working with schools and care providers to communicate what is known about a child’s medically defined needs may help manage and lessen symptom triggers. Ensuring that all parties involved in a child’s care are appropriately informed, and that clear collaboration exists between families, carers, educators and activity providers can also promote wellbeing without unnecessary restriction or isolation, while still supporting early recognition of changes in a child’s health so that appropriate support can be provided.

• Discuss activities and environments that may influence symptoms: Maintain an open and collaborative approach to practical adjustments that may support participation, rather than avoiding activities altogether where reactivity may be a consideration. Where available, families may provide a list of  both well-tolerated activities and those that may contribute to symptoms.Care providers may benefit from checking with families before introducing new or commonly used products or activities. Examples may include dress-up activities, shared costumes or craft smocks, sensory play stations (such as slimes or textured materials), exposure to heat, and the use of sunscreens, soaps or wipes.
• Support two-way sharing about symptom presentation: As both families and school or care providers spend extensive time with children throughout the day, regular communication is valuable and can help detect subtle changes that may warrant medical support. It may be helpful for care providers to report to families on any new or changing symptoms or behaviours, such as increased fatigue, reduced participation or activity avoidance. Families may also choose to share information about new strategies introduced at home to manage or reduce symptom risk, with similar approaches considered in care or school environments.
• Be aware of medical safety considerations: Ensure up-to-date information is available regarding the child’s known diagnoses, including any secondary or co-occurring conditions such as asthma or food allergies, as well as any medically prescribed management of symptoms. Where a child has a diagnosis of anaphylaxis, care or school settings should ensure a current ASCIA Action Plan is accessible and that relevant staff have received appropriate training in recognising reactions and administering the child’s prescribed adrenaline. Where asthma is present, sharing asthma management plans and ensuring appropriate training are also important.
• Support the child to access help when needed: Where appropriate for the child’s age and development, ensure the child knows who their key support people are within the care, school or activity setting, so assistance is readily available if symptoms arise.

For more information on MCAS, visit TAMS website.

Citations

1. Diagnosis and management of patients with mast cell activation syndromes: status 2026
2. Position Paper – Diagnosis and Investigation of Mast Cell Activation Disorders and Syndrome
3. Management of mastocytosis and mast cell activation in children
4. The role of mast cells in pediatric gastrointestinal disease
5. Mast cell activation syndrome
6. Global Classification of Mast Cell Activation Disorders: An ICD-10-CM–Adjusted Proposal of the ECNM-AIM Consortium
7. Mast Cell Activation Syndrome: Proposed Diagnostic Criteria
8. Effect of Gender and Special Considerations for Women in Mastocytosis and Anaphylaxis.
9. Scroll, Like, Diagnose? Evaluating MCAS Information on TikTok
10. Mastocytosis
11. Pediatric Mast Cell Disorders: Facts in Brief
12. Mast Cell Activation Syndrome in Children: A Nuanced Approach to Diagnosis and Patient Care: A Narrative Review Illustrated by Two Case Reports
13. Best practice guidelines for anaphylaxis prevention and management in children’s education and care