What is the Difference Between MCAS and Histamine Intolerance

The key difference between MCAS and histamine intolerance is that MCAS is an immunological condition where mast cells inappropriately release excessive chemical mediators, while histamine intolerance is a condition where dietary histamine accumulates in the body.

Histamine is a nitrogenous compound involved in local immune responses in the human body. It also regulates physiological functions, acting as a neurotransmitter for the brain, spinal cord, and uterus. It was discovered in 1910. Since then, it has been considered a local hormone. As an integral part of the immune system, histamine may be involved in immune system disorders such as MCAS. It also may be involved in histamine imbalance conditions like histamine intolerance. MCAS and histamine intolerance are two conditions that can occur due to over-accumulation of histamine in the body.

CONTENTS

1. Overview and Key Difference
2. What is MCAS 
3. What is Histamine Intolerance
4. Similarities – MCAS and Histamine Intolerance 
5. MCAS vs Histamine Intolerance in Tabular Form
6. Summary – MCAS vs Histamine Intolerance 

What is MCAS?

Mast cell activation syndrome (MCAS) is a type of mast cell activation disorder and an immunological condition where mast cells inappropriately release excessive chemical mediators. These chemical mediators include leukotrienes, histamines, prostaglandins, and tryptase. There are no known causes for this disorder, but it appears to be inherited in some patients. This condition may be mild. However, it can exacerbate due to stressful life events. The symptoms include flushing, hives, itchiness, light-headedness, diarrhoea, nausea, congestion, coughing, and anaphylaxis.

Figure 01: MCAS

MCAS is still a poorly understood condition. Furthermore, it is a current topic of research.  This condition can be diagnosed in the laboratory by measuring elevated mast cell mediators. MCAS is often difficult to identify due to the heterogeneity of symptoms. The World Health Organisation has not yet published diagnostic criteria for MCAS. The treatment methods include mast cell stabilizers (cromolyn sodium), H1-antihistamines (cetirizine), H2-antihistamines (ranitidine), antileukotrienes (montelukast), and non-steroidal anti-inflammatory drugs.

What is Histamine Intolerance?

Histamine intolerance is a condition where dietary histamine accumulates in the body. The intolerance is caused usually by the gradual accumulation of extracellular histamine due to an imbalance. People naturally produce histamine along with an enzyme that is responsible for breaking histamine: diamine oxidase. Diamine oxidase deficiency causes the inability of histamine breakdown leading to histamine intolerance. The symptoms include headaches, nasal congestions, fatigue, hives, digestive issues, irregular menstrual cycle, nausea, vomiting, abdominal cramping, tissue swelling, irregular heart rate, anxiety, difficulty regulating body temperature, and dizziness.

Figure 02: Histamine Intolerance

Roughly 1% of the population has histamine intolerance. Of those, 80% are middle-aged people. There are some food items such as alcohol, fermented foods, dried fruits, avocados, eggplants, spinach, shellfish, aged cheese, etc., high in histamine, which can trigger inflammatory reactions. The prick test can be used to diagnose histamine intolerance. The treatment methods include antihistamines, topical steroid creams for rashes and supplements to reduce histamines such as vitamin C, B6, Zn, Cu, magnesium, quercetin, DAO promoters.

What are the Similarities Between MCAS and Histamine Intolerance?

• MCAS and histamine intolerance are two conditions that can occur as a result of over-accumulation of histamine in the body.
• In both conditions, the patients have a normal number of mast cells in the body.
• They cause similar symptoms such as rashes, hives, etc.
• Antihistamines can be used to treat both conditions.

What is the Difference Between MCAS and Histamine Intolerance?

MCAS is a type of mast cell activation disorder which is an immunological condition where mast cells inappropriately release excessive chemical mediators, while histamine intolerance is a condition where dietary histamine accumulates in the body. So, this is the key difference between MCAS and histamine intolerance. Furthermore, in MCAS, the mast cells are hyper-responsive, whereas, in histamine intolerance, the mast cells are not hyper-responsive.

The following infographic lists the differences between MCAS and histamine intolerance in tabular form for side by side comparison.

Summary – MCAS vs Histamine Intolerance

Histamine is a nitrogenous compound involved in local immune responses in the human body. MCAS and histamine intolerance are two conditions of over-accumulation of histamine in the body. MCAS is an immunological condition where mast cells inappropriately release excessive chemical mediators, while histamine intolerance is a condition where dietary histamine accumulates in the body. Thus, this is the summary of the difference between MCAS and histamine intolerance.

Reference:

1. M. Frieri. “Mast Cell Activation Syndrome.” Clinical Reviews in Allergy & Immunology, U.S. National Library of Medicine
2. “Histamine Intolerance: SYMPTOMS, Diet & Treatment.” Amy Burkhart, MD, RD, 11 May 2021.

Image Courtesy:

1. “Blausen 0018 Anaphylaxis” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014” WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia
2. “Rash” By Enochlau – Own work (CC BY-SA 3.0) via Commons Wikimedia

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