Mast cells are immune cells that release histamine and other mediators during allergic reactions and defence responses. Mast cell activation syndrome (MCAS) describes recurrent episodes of systemic mast-cell activation in which these mediators cause clinically relevant symptoms in more than one organ system.
Fatigue, brain fog, food reactions, or palpitations can occur in MCAS, but they are common in many other conditions and do not diagnose MCAS on their own. A careful assessment helps avoid attributing every complex symptom pattern to mast cells without sufficient evidence.
Compatible episodes usually involve two or more systems at the same time or repeatedly. Possible manifestations include:
Acute breathing difficulty, swelling of the tongue or throat, fainting, or signs of anaphylaxis require emergency care. People with a known risk should have an individual emergency plan and, where prescribed, adrenaline auto-injectors.
Consensus criteria require three components: first, typical recurrent episodes affecting at least two organ systems; second, objective evidence of mediator release during an episode; and third, a clinically relevant response to medication that blocks mediators or stabilises mast cells. The preferred laboratory marker is serum tryptase measured during an episode and compared with a stable baseline. A rise of 20% plus 2 ng/mL over baseline is the established criterion for systemic mast-cell activation.
Tryptase should be taken as soon as possible during an episode and repeated when the person is well. A normal baseline does not by itself exclude a reaction, while a persistently raised value may have other explanations. Urinary mediator measurements can be helpful in selected cases, but sampling and interpretation require experience.
Allergies, chronic urticaria, asthma, medication reactions, infections, endocrine disorders, gastrointestinal disease, autonomic dysfunction, anxiety disorders, and other conditions can cause overlapping symptoms. Mastocytosis and hereditary alpha-tryptasaemia require different diagnostic pathways. We therefore review the history, medication, triggers, examination findings, and available laboratory results in context.
Some people with Long COVID, ME/CFS, or post-infectious fatigue report symptoms that overlap with mast-cell mediator effects. This overlap is not proof that MCAS is the cause. The evaluation should remain open to other mechanisms and focus on findings that can guide safe, useful care.
When the diagnosis is supported, treatment begins with an individual review of avoidable triggers and emergency planning where necessary. Depending on the symptoms and medical history, a physician may consider H1- and H2-antihistamines, leukotriene-modifying medication, mast-cell stabilisers, or other measures. The choice, dose, and monitoring are individual; medication should not be started or changed without medical advice.
Very restrictive diets are not a substitute for assessment and can lead to nutritional problems. A food-and-symptom diary may help identify patterns, but it does not establish an MCAS diagnosis. Any dietary change should be realistic and professionally supervised when symptoms are severe or food intake is limited.
The consultation in Munich makes time for the course of episodes, possible triggers, previous diagnoses, current medication, and available reports. The aim is a transparent assessment and a plan that reflects both medical evidence and the person's everyday limitations.