Mast Cell Activation Syndrome (MCAS), Histamine and Dermatitis

Mast Cell Activation Syndrome (MCAS) is a complex condition that has been gaining attention in the medical community for its role in a variety of symptoms and diseases, including skin conditions such as eczema and dermatitis. (1–3)

This article aims to shed light on what MCAS is, how it’s diagnosed, its connection to skin conditions and potential management strategies.

What is MCAS?

Mast Cell Activation Syndrome, or MCAS, is a condition where mast cells, a type of white blood cell that play a crucial role in the body’s immune response, behave abnormally, triggering immune related symptoms.

Mast cells play a pivotal role in the management of inflammatory responses, acting as the defensive guardians against pathogens. These cells are found in tissues throughout the body, especially where the body is exposed to contact with foreign bodies, such as the skin, lungs, and digestive tract.

When mast cells detect a foreign substance or an injury they release a variety of different chemical signals including histamine, cytokines, and growth factors, which are all part of the body’s defence systems. This is normal and what keeps us healthy.

Normally, mast cells help protect the body from disease and aid in wound healing but in MCAS these cells are overly sensitive and release too many of these chemicals leading to a range of symptoms that can affect every part of the body, including the skin, gastrointestinal, cardiovascular, respiratory and neurological systems. Long COVID is also thought to involve aspects of MCAS.

Symptoms and Diagnosis

The range of symptoms involved in MCAS are vast and can vary significantly from one individual to another. Reported symptoms include: flushing, itching, urticaria (hives), stomach pain, nausea, vomiting, diarrhoea, low blood pressure, headaches and breathing issues. The severity of symptoms can range from mild to life-threatening.

As you can tell these are symptoms that can overlap with many other conditions making diagnosis tricky. Officially there are three sets of criteria needed for MCAS diagnosis:

1. Severe, recurrent symptoms of mast cell activation in at least two organ systems.
2. Laboratory proof that mast cell levels are high
3. Response to mast cell mediator targeting therapy such as antihistamines.

The MCAS, Dermatitis Connection

The skin is one of the organs most commonly affected by MCAS and dermatitis (atopic, contact and urticaria) is the most common skin illness linked to this condition.

Dermatitis, characterised by inflammation of the skin, can be exacerbated by the overactive release of histamine and other chemicals from mast cells, leading to redness, itching, and swelling, all symptoms so characteristic of this chronic skin condition.

The different types of eczema/dermatitis have multifactorial root causes including genetic, environmental and immune system factors. The link between MCAS and dermatitis is found within the immune system, particularly in how mast cells can over secrete the chemicals that can exacerbate an existing flare or trigger a new one. A combination of MCAS with chronic, relapsing dermatitis can cause misery for sufferers.

Histamine, one of the most well-known mediators released by mast cells, is involved in immediate allergic reactions and plays a significant role in vasodilation or increased blood flow, and recruitment of other immune cells to the site of injury or infection. If you are interested in learning more about histamine, I have written a series of 5 articles relating to histamine, which can all be found via my website.

Understanding the role of mast cells in immune responses and their contribution to conditions like MCAS and dermatitis underscores how intertwined both the immune system and skin health is. What is important to bear in mind is the need for support that may modulate mast cell activity but also alleviate the dermatitis symptoms.

Management strategies for MCAS-Related Dermatitis

Managing diagnosed MCAS and dermatitis needs a rounded approach that takes into account both the overactive mast cells and the dermatitis symptoms. Here are some tips that may help:

Identification and avoidance of triggers. Keep a food, environment and symptom diary. Monitor what appears to be triggering your own personal symptoms. These could be foods, alcohol, temperature change, stress or many other things.
Diet and nutrition. Keeping your histamine levels low by following a lower histamine diet can be helpful for some. However, eliminating too many foods can lead to further restrictions and can be problematic in the long term. If you want to follow an elimination diet please work with a nutrition or health practitioner.
Stress management. Stress is a major mast cell trigger, so keeping your stress levels low is vital. Think about incorporating a daily meditation or yoga practice or even making time to do a hobby that brings you joy.

In summary, MCAS is a multifaceted condition that can significantly impact the physical and mental wellbeing of affected individuals. Having a medical diagnosis that then provides an appropriate treatment plan that alleviates symptoms is important, however, understanding the root cause of the hyper-activation be it food, environmental, lifestyle factors or stress is vital for long-term health.

Histamine & MCAS Strand – calm reactive skin and sudden flare-ups

If your eczema flares quickly after certain foods, stress, or environmental changes, histamine and mast cells may be involved. This strand helps you understand how histamine works in the body and why some people experience intense itching, redness, or swelling when these pathways are overstimulated.

Over 5 weeks (or in your own time), you’ll learn how to lower your histamine load, spot patterns in your symptoms, and support your body’s natural histamine clearance. With a dedicated low-histamine recipe booklet and daily guidance, you’ll reduce reactivity and help your skin stay calmer for longer.

What you’ll get:

• 5 weeks of modules on histamine and mast cell activation
• Food lists, symptom trackers, and handouts for daily use
• A tailored low-histamine recipe booklet (21 breakfasts, 21 lunches, 21 dinners, 7 snacks)

Who it’s for: Anyone with eczema that flares suddenly and severely, especially after certain foods, alcohol, stress, or environmental triggers.

References.

Mihele DM, Nistor PA, Bruma G, Mitran CI, Mitran MI, Condrat CE, et al. Mast Cell Activation Syndrome Update—A Dermatological Perspective. J Pers Med. 2023;13(7).
Frieri M. Mast Cell Activation Syndrome. Clin Rev Allergy Immunol [Internet]. 2018;54(3):353–65. Available from: https://doi.org/10.1007/s12016-015-8487-6
Theoharides TC, Perlman AI, Twahir A, Kempuraj D. Mast cell activation: beyond histamine and tryptase. Expert Rev Clin Immunol [Internet]. 2023 Jun 3;19(6):639–54. Available from: https://doi.org/10.1080/1744666X.2023.2200936