Mast Cell Activation Syndrome (MCAS) and Eating Disorders: Uncovering a Complex Connection

Mast Cell Activation Syndrome (MCAS) is a complex, often misunderstood condition involving dysregulation of the immune system. Increasingly, clinicians and researchers are observing that some individuals with eating disorders also present with symptoms consistent with MCAS—posing important questions about overlapping symptoms, misdiagnoses, and integrated treatment approaches.

This article explores the emerging connection between MCAS and eating disorders, outlining the mechanisms, challenges, and recommendations for providers, patients, and families navigating both conditions.

What Is Mast Cell Activation Syndrome (MCAS)?

MCAS is a disorder of mast cell dysregulation in which mast cells release mediators—like histamine, tryptase, cytokines, and prostaglandins—inappropriately or excessively. These mediators can affect nearly every system in the body, leading to multi-systemic symptoms that fluctuate over time.

Common symptoms include:

• Gastrointestinal distress (nausea, diarrhea, bloating, abdominal pain)

• Skin rashes, flushing, or hives

• Headaches or migraines

• Dizziness or tachycardia (often overlapping with POTS)

• Food intolerances or allergic-like reactions

• Fatigue, anxiety, and brain fog

While MCAS can mimic allergic reactions, it does not follow a traditional IgE-mediated allergy pattern, which makes it difficult to diagnose using standard allergy testing.

Sources: Afrin et al. (2016), Theoharides et al. (2020)

How Might MCAS Relate to Eating Disorders?

Although the link between MCAS and eating disorders is not fully understood, several overlapping features may contribute to a bidirectional or co-occurring relationship.

1. Gastrointestinal Distress Can Lead to Food Avoidance

The GI symptoms common in MCAS—bloating, pain, nausea, and diarrhea—may lead individuals, particularly children and adolescents, to begin restricting their diet to avoid discomfort. Over time, this can evolve into Avoidant/Restrictive Food Intake Disorder (ARFID) or other restrictive patterns.

Many patients report that their initial food restriction was not about body image, but about avoiding intense physical discomfort.

2. Heightened Sensory Sensitivities

People with MCAS often report sensory issues with taste, texture, and smell, which can further limit food choices and mimic or contribute to disordered eating patterns. Sensory processing challenges are also common in individuals with autism spectrum disorder (ASD), another population with high rates of ARFID.

Source: Kushner (2021), Journal of Pediatric Gastroenterology and Nutrition

3. Histamine and Neuropsychiatric Symptoms

Histamine and other mast cell mediators can cross the blood-brain barrier, potentially contributing to anxiety, depression, and disordered thinking. These symptoms can reinforce compulsive or restrictive behaviors common in eating disorders.

This neuroinflammatory connection may help explain why some eating disorder patients with MCAS experience significant anxiety, obsessive thoughts, or trauma-related responses.

Source: Theoharides et al. (2019)

4. Shared Comorbidities and Dysautonomia

Many patients with eating disorders—particularly those with ARFID or atypical anorexia—also present with POTS (Postural Orthostatic Tachycardia Syndrome), Ehlers-Danlos Syndrome (EDS), or functional GI disorders. These conditions often overlap with MCAS, suggesting a shared physiological vulnerability involving connective tissue, the autonomic nervous system, and immune dysregulation.

Source: Raj et al. (2018), Bonilla et al. (2015)

The Diagnostic Challenge

Diagnosing MCAS in individuals with eating disorders is difficult for several reasons:

• Symptoms may be attributed solely to the eating disorder (e.g., weight loss causing GI issues)

• Food restriction may reduce mast cell symptoms temporarily, confusing the clinical picture

• Labs used to diagnose MCAS (e.g., tryptase, prostaglandins) can be time-sensitive and inconsistent

• Providers may be unfamiliar with MCAS or may assume symptoms are psychosomatic

A collaborative, multidisciplinary approach—including immunology, gastroenterology, psychiatry, and nutrition—is often essential for accurate diagnosis and management.

Treatment Considerations

1. Medical Management of MCAS

• Antihistamines (H1 and H2 blockers)

• Mast cell stabilizers (e.g., cromolyn sodium)

• Low-histamine or elimination diets—with close nutritional supervision to avoid worsening restriction

• MCAS-specific supplements (e.g., quercetin, DAO enzyme)

Medical treatment must be carefully integrated with eating disorder care to avoid reinforcing avoidance or control-based behaviors.

2. Psychological Support

• Trauma-informed therapy that addresses somatic symptoms and food-related fear

• ARFID-informed treatment if applicable

• Psychoeducation to reduce anxiety around symptoms and promote trust in the body

3. Nutritional Rehabilitation

• Collaboration with a dietitian skilled in both eating disorders and food sensitivity protocols

• Focus on expanding safe foods and reducing restriction gradually

• Monitor for nutrient deficiencies and signs of malnutrition

Key Recommendations for Providers

• Screen for MCAS when patients present with multi-system symptoms, food intolerance, or ARFID-like restriction

• Validate symptoms without jumping to psychogenic explanations

• Collaborate with specialists and avoid extreme elimination diets unless medically necessary

• Support families in understanding that medical symptoms and disordered eating can coexist

• Avoid blaming or minimizing—patients with MCAS may already feel dismissed or disbelieved

Final Thoughts

The intersection of MCAS and eating disorders is still an emerging area, but what’s clear is that complex, multi-system conditions require nuanced, integrative care. For many patients, validating their physical symptoms and understanding the impact of mast cell dysregulation can be a turning point in both medical stabilization and psychological recovery.

By recognizing the role of MCAS in disordered eating—especially when it leads to fear, restriction, or anxiety around food—clinicians can build a bridge between physical healing and full recovery.

References

• Afrin, L. B. (2016). Never Bet Against Occam: Mast Cell Activation Disease and the Modern Epidemics of Chronic Illness and Medical Complexity.

• Theoharides, T. C., et al. (2019). Mast cells and inflammation. Biochimica et Biophysica Acta, 1865(1), 94–100.

• Raj, S. R., et al. (2018). Postural tachycardia syndrome (POTS). Circulation, 138(8), 865–867.

• Kushner, B. J. (2021). Sensory processing and feeding difficulties in children. JPGN Reports, 2(3).

• Bonilla, F. A., et al. (2015). Consensus statements on the diagnosis and treatment of mast cell disorders. Journal of Allergy and Clinical Immunology, 136(2), 350–356.

• Theoharides, T. C., et al. (2020). Neuropsychiatric aspects of mast cell activation. Translational Psychiatry, 10(1), 1–15.