Is It Really Anxiety? Or Could It Be MCAS?

Most people have never heard of mast cell activation syndrome (MCAS)—yet research suggests that as many as 1 in 6 people may be living with it.

Even more surprising? MCAS is often mistaken for a mental health issue, especially in people who present with symptoms like brain fog, anxiety, insomnia, or emotional dysregulation.

Here’s what MCAS can actually look like:

  • Brain fog that feels like dissociation or depression

  • Irritability or mood swings with no obvious trigger

  • Sensitivity to light, sound, smell, or texture

  • Insomnia, night-time panic, or waking up with a racing heart

  • Shortness of breath, a lump in your throat, or feeling like you cannot relax

  • Unrelenting fatigue or muscle pain

  • Social withdrawal due to unpredictable symptoms

  • Nausea, abdominal pain, or unexplained gastrointestinal (GI) distress

  • Lack of positive response to psychiatric medications or psychotherapy

These symptoms often get written off as anxiety, trauma responses, attention-deficit/hyperactivity disorder (ADHD), or mood disorders like depression. And sometimes, those conditions are also present. But for people with MCAS, there is a cause for these symptoms: immune system dysfunction.

What Is MCAS, Really?

In MCAS, mast cells—a type of immune cell—release excessive chemicals like histamine into the body. This can affect nearly every organ system, leading to a mix of neurological, cardiovascular, gastrointestinal, and skin symptoms.

The trouble is, MCAS doesn’t always follow a clear pattern. Symptoms may come and go, or worsen in response to heat, stress, foods, medications, or hormones. That makes it hard to identify—and even easier to misdiagnose.

Why MCAS Is So Often Confused with Mental Health Conditions

MCAS can cause:

  • Low mood or depression

  • Restlessness or irritability

  • Panic attacks or a racing mind

  • Sleep disturbances

  • Brain fog and memory problems

While these look like psychiatric symptoms, they stem from immune dysregulation. That’s why traditional mental health treatments often fall short for people with MCAS.

The Problem with Missed Diagnoses

When MCAS goes unrecognized, people may spend years:

  • Trying multiple medications that do not help

  • Internalizing their symptoms as personal failures

  • Wondering if their distress is “all in their head”

  • Being dismissed or misdiagnosed in clinical settings

Worse yet, symptoms may continue to progress if the cause of them—mast cell dysfunction—is never addressed.

Getting the Right Diagnosis and Treatment

MCAS can be diagnosed—but only if a healthcare provider knows how to look for it. This often involves:

  • Tracking symptom patterns over time

  • Identifying triggers (like heat, stress, or certain foods)

  • Lab testing for markers of mast cell activity (like histamine or tryptase), but recognizing that lab testing for MCAS is flawed and can easily miss the diagnosis

  • Trialing medications such as mast cell stabilizers, antihistamines, or low-histamine diets for symptom relief

Treatment is highly individualized—but when MCAS is correctly identified, many people see significant relief.

Why Awareness Matters

MCAS is still underdiagnosed and misunderstood, despite growing recognition in specialties like allergy, immunology, and functional medicine.

Raising awareness means fewer people are told their symptoms are caused by a mental health condition. It means more people get access to the right care. And it means those struggling with unexplained symptoms might finally feel validated—and start to feel better.

Could MCAS Be the Missing Piece?

If you have been told your symptoms are psychiatric but you just don’t feel like that’s the whole story, MCAS might be worth exploring. No one should feel dismissed for symptoms that do not fit neatly in a box.

It is time we stop ignoring the immune system’s role in emotional and physical health—and start asking better questions about what is really going on.


Want expert tips for living well with MCAS?

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PMID: 38003876; PMID: 32328892

Disclaimer: This blog post is for informational purposes only and shall not be construed as behavioral health or medical advice. It is not intended or implied to supplement or replace treatment, advice, and/or diagnosis from your own qualified healthcare provider.

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