Mast Cell Activation Syndrome (MCAS) and Histamine Intolerance (HI) are both conditions related to histamine dysregulation, but they have different underlying mechanisms and clinical features.
Key points:
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Definition: MCAS is primarily an immune system disorder where mast cells are hyper-activated and release excessive amounts of chemical mediators, including histamine. HI is primarily a metabolic issue where the body has difficulty breaking down and eliminating histamine, which leads to histamine levels exceeding the body's capacity.
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Mechanism: In MCAS, mast cells become hyper-responsive and release their contents inappropriately, even in the absence of a real threat. In HI, there is a deficiency or dysfunction of enzymes involved in histamine metabolism, such as diamine oxidase (DAO).
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Triggers: MCAS triggers can include stress, infections, certain foods, medications, and environmental exposures. HI triggers are typically allergens, or medications that interfere with DAO.
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Symptoms: MCAS can cause many symptoms, from slow allergy-like reactions to fast anaphylactoid shock, and can be unpredictable and vary from person to person. HI symptoms often resemble an allergic reaction, and typically occur after consuming histamine-rich foods or substances that inhibit DAO.
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Treatment: MCAS treatment emphasizes mast cell stabilizers and limbic system recovery, along with addressing probable causes such as toxins or infections. HI treatment emphasizes low-histamine foods and DAO supplements. Both MCAS and HI use symptom-specific medications such as antihistamines.