The root causes of MCAS

So, what are the root causes of MCAS?


Well, there can be many, which means trying to find the root causes of MCAS can be tricky.

Finding out that you have mast cell activation syndrome is hard enough, let alone trying to work out how it all started to help you heal, how you are going to manage it or seeing posts on the internet of how people who have it are becoming sicker, and they have no hope because they don’t know what to do.

Trying to find support and information on the condition can be overwhelming, or you may be pleased that you have finally got a diagnosis, which means you can concentrate on what are the root causes of MCAS in you. You finally have a starting point after years of being told there is nothing wrong, with tests all normal and that it is all in your head.

The root causes of MCAS

This is a harmful belief; MCAS is a real and challenging condition. When you hear this, it can be very upsetting. They don’t understand how challenging it is to deal with just daily tasks. People with MCAS should be taken more seriously, and NOT told that their symptoms are in their heads. They deserve to be listened to and understood and to get the support and respect that they deserve. The condition is hard enough without having to keep proving yourself to everyone. 

Mast cells are in most tissue in the body, they are part of the immune system, they help to protect against invaders and to heal wounds, but when you have MCAS the cells overreact, releasing too much inflammation which can cause you to have many symptoms. Brain fog, Hives, digestion issues, fatigue, body pain, reactions to food, smells, chemicals and many many more, but what are the root causes of MCAS? This is the big question.

When looking into what is the root cause of MCAS it can be many things, with this condition everyone is unique and everyone’s symptoms are different. A medication that works for one person will not necessarily work for another. Some people do well on supplements alone, and others may not be able to even tolerate them. Everyone is different with MCAS and that includes how they ended up with it in the first place.

Leaving aside the root causes of MCAS for a moment, how did you get MCAS? Well, this is another tricky area, as some will say that it is just in your genes, whereas others say that it can be triggered by exposure to mould etc., yet if you go to the doctors and tell them you have got it through the mould, for example, they will look at you as though you are crazy.

So, what are the root causes of MCAS (mast cell activation syndrome)?

Mould, heavy metals, infections such as candida, bacterial overgrowth, parasites or Lyme Disease; these underlying triggers can keep the immune system on constant alert. These trigger mast cells easily, causing you to flare.

From the research, I have carried out and through speaking to various experts, it would appear that mould seems that it could be one of the root causes of MCAS and a big part of the equation. Mould releases mycotoxins that have a huge impact on the body. Chronic mould exposure will cause the mast cells to keep releasing histamine and other chemicals to attack the toxins.

Mould can be a root causes of MCAS

If you continue to be in an environment with mould, your body will stay in a chronic state of inflammation and will be in a constant state of defence. The most common illness associated with mould is CIRS which is Chronic Inflammatory Response Syndrome, but MCAS is another of the conditions triggered by mould. 

It is particularly important, that if you have been exposed to mould or are living with mould in your home, that you get it sorted. If you are experiencing symptoms of histamine intolerance or MCAS, it’s important that you get tested for mould and all other underlying triggers such as infections and heavy metals if you are not improving.

Working with a Functional Medicine Doctor who specialises in this condition is very important. There are a lot of practitioners out there that will not understand the condition, and they can potentially make you a lot worse. Patients with MCAS need to go very slowly, as they can be extremely sensitive and need to have the right gentle supplements to help them recover.

Food Triggers

Eating the wrong food is a common problem for people with MCAS. So many people don’t realise what impact food can have on them, in turn making them considerably worse.

It is not just high histamine foods like coffee, alcohol, fermented foods, chocolate, vinegar, pickles, cured meats, dairy foods such as kefir, aged cheese, yeast, fish and shellfish, aged food, and citrus foods but also healthy foods like spinach, avocado, strawberries also some nuts.

The triggers that cause of MCAS

There are other things to look out for when identifying the root causes of MCAS –

  • Packaged food – You don’t know how long it has been sitting there. They can also contain additives, which can be another trigger.
  • Leftovers – When food is left, the histamine will become high very quickly. It must be frozen as soon as possible.
  • For some people, it’s not just histamine in food that is a problem. There are also oxalates, salicylates and lectins that can be a problem too.

Genetic Factors

This can be a crucial part and potentially one of the root causes of MCAS. If your body isn’t detoxing and working the way it should be. Having the appropriate tests will allow you to see what areas are going wrong in your body and how best to support them. If you have a genetic weakness, you can be affected by the toxins in the world. 

We are exposed to chemicals all the time. They are in our food, the water we drink, cleaning products, makeup, skincare and even the air that we breathe. If your body isn’t detoxing properly and you are not giving it the proper support, then you may be preventing yourself from getting better. This was an important part of my healing process and is something that you would need to do with a Functional Medicine Practitioner.


Hormones can also be a part of what is causing your mast cells to play up. Women tend to suffer more from this condition than men. Oestrogen causes the mast cells to release histamine. This is why you will probably notice that you have increased symptoms at different times of the month. It can also affect ladies who are going through menopause, as their hormones change.

Cortisol is another important hormone. Adrenals make cortisol which regulates the immune system and gives you energy. If you are stressed, have been ill for a long time and your body is in constant fight or flight, cortisol can get out of balance, which is often called Adrenal Fatigue.


Stress can have a massive impact on our health and can be key when looking for the root causes of MCAS. It can even change the genetic expressions of genes.  Everyone experiences stress in their lives, but it is how we deal with it that is key.

Reducing stress is a big part of your healing. How you deal with situations and circumstances, getting support, being out in nature, meditating and whatever works for you to help you. You can address all of the things above, but if you are still living with chronic stress, it will stop you from healing.

Stress can cause MCAS


When you have experienced trauma, it can put your body into fight or flight mode. Anyone can experience trauma and it can be either from when you were a child or as an adult. It might not be something that you think much of, or it might be something that has caused you extreme stress, which can make your body feel like it is under constant attack.

It is particularly important to address trauma, as emotions may surface even years later. These emotions/feelings including – stress, anger and feeling scared or sad can cause the mast cells to release more histamine.

It is common to feel unsafe in your own body, in relationships and in the world in general if the trauma has not been processed and understood. Working with a therapist can help you deal with this.

Trauma can be a root cause of MCAS

So, what is the root cause of MCAS? Well, as you can see it could be a number of things, either individually or in combination. Therefore, finding the root cause for you personally is a puzzle which needs solving. It can be a long and complicated process but rest assured, with the right help and support, it is possible for you to get your life back.

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