Mast Cell Activation Syndrome (MCAS) - Gluten Free Guerr...

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Mast Cell Activation Syndrome (MCAS)


Hi, on my quest to figure out why many foods reacting in the same way as gluten (is it hidden gluten, is it intolerance to any ppms, is it SIBO, etc.?) I stumbled on lots of information on histamine intolerance, and how this fits many of the issues I've been having (also noticed antihistamines took 'sting out of the tail' of the reactions I was having). Another poster had mentioned histamine intolerance also, in relation to SIBO. Today, on a separate minor 'ah ha' moment (apple juice that resulted in no reaction), I stumbled on to something called Mast Cell Activation Syndrome. This is an emerging area that seems to encompass many of the random immune symptoms and reactions a lot of people have that are ignored/disregarded by medics, but all add up to the underpinning issue of over production of histamine due to Mast Cell Activation Syndrome. It seems to go hand in hand with a lot of autoimmune conditions, so if you are seeking answers to random symptoms you're experiencing beyond the obvious coeliac ones or having a lot of cross-reactive foods , worth checking this out. Lots of information on basic Google searches, but this research paper is specifically for coeliac and MCAS: which is a bit of a heavy read. A more user friendly resource for general information on MCAS is this one: and is a lot more comprehensive and wide ranging than the NHS online resource for MCAS which limits to a specific type of MCAS called mastocytosis This one is related to Lymes Disease but quite helpful info: . So, I can now offer 3 avenues of exploration for anyone struggling with random issues that won't resolve even though following GF diet:

1. SIBO (both hydrogen and methane dominant types of SIBO)

2. HIT (Histamine Intolerance, which may be underpinned by SIBO, but also linked to coeliac damage, etc)

3. MCAS (Mast Cell Activation Syndrome)

12 Replies

Thanks Mise, that is really interesting and could explain a lot of what is going on for many people.

Hi Mise.

I’m fairly new to the forum. Great info thanks. Im a research scientist and love reading the journals.

I’m familiar with histamine intolerance and the low histamine diet which helps tremendously with weird symptoms that often can’t be pinpointed but food related. I’ve been on low histamine diet strictly and it does help a lot. Then I reintroduced some foods that were on avoid list think I found my threshold. It takes a long time but is worth it. I’m still working on issue I have with my gut health though. So I think many things can be at play. Ultimately all seems to come back to gut heath and the microbiome.

Are you familiar with Dr Janice Joneja? She’s the authority on the low histamine diet. And the one who has done so much research on histamine intolerance. She has a few books on histamine intolerance. Well worth a read. And a cookbook came out most recently. Great books. A wealth of free info on histamine intolerance on .


Hi Mise

This is very interesting to me. I was diagnosed with coeliac disease nearly 5 years ago after falling very ill. Over the past few months l have noticed that even if l lightly scratch my skin, or if l get hot and my clothes rub on my skin, l get really red marks which are intensely itchy and take about half an hour to calm down. I have tried antihistamines which help a bit with the irritation but the condition does not go away. When l googled this it is a condition which is called dermatographia. I was trying to find out if this was linked to coeliac disease and l think it is more common in people with autoimmune diseases. In normal times l would have gone to see the nurse at my doctor's surgery, but in these times l have not gone. Would be interesting to see if anyone else suffers from this. Think l will have a look on the site that Researchfan recommends.

Mise in reply to Shirleywhirl

Hi Shirleywhirl. Skin irritation/rashes do seem to be one of the key issues linked with histamine intolerance/Mast cell activation. It's worth giving the low histamine diet a bash for a while. Apparently MAST does have a diagnostic approach, but dietary change is a good way of figuring out what does and doesn't work. Still worth chasing an appoinment for your rash issue, but interesting anti-histamines help a bit.

Mise in reply to Researchfan

Hi Researchfan.

No, I hadn't heard of that author, but will be checking her out. Thank you for that recommendation.

Yes, all roads lead to Rome and diet/gut health just seems to be the core of so much and the failure of our mainstream doctors to really grasp this seems very backward looking.

I've had a really good dietician who I found privately, and in looking at the diet she recommended it does seem she was looking at the histamine issue also.

If I can ask, beyond gut issues, what were the random other symptoms you were having?

Researchfan in reply to Mise

Hi Mise. Thanks for reply.

Yes. Beyond gut issues, the main ones mental fogginess and fatigue, headache, anxiety, and painful menstrual periods.

It was actually in my quest to heal my periods that I came across histamine intolerance a few years ago ( can be a cause of dysmenorrhea, related to hormones too).

I found the low histamine diet really helped in addition to an antihistamine when needed.

There’s also some really good info on histamine intolerance by Dr Georgia Ede at


Mise in reply to Researchfan

Great. Thank you for that. Great that it worked.

I thought my daughter (has Celiac) might have MCAS (that's the abbreviation I'm used to seeing) so I took her to mast cells specialist who diagnosed her with oral allergy syndrome. About the same time as she became ill I started having typical MCAS/histamine intolerance issues (hives, itching, etc.). I did not bother with trying to get diagnosed with MCAS as it is almost impossible in US with current diagnostic criteria unless you have hereditary alpha tryptasemia. I did a phone consult with this doctor: She was very helpful; she noted in her case she had become sensitive to sulfites.

In addition to all the usual stuff for MCAS/ histamine intolerance, my daughter and I have had some benefit from using stand-alone HEPA air filter units (and we upgraded the HVAC filters).

I expect more research on this as some covid long-haulers are reporting MCAS-like symptoms.

Mise in reply to Rhyothemis

Thanks Rhyothemis.

You're correct in abbreviating to MCAS - my error is calling it MAST. It does seem that getting diagnosis is difficult as the recognition is more of a recent thing, and I can't imagine the UK is any more up to speed than the US. It's interesting you managed to find a specialist.

From my own perspective it does add up a lot of odd occurences over the years, including very strong allergic reactions to certain medications and food items, which seem to be the classic one for MCAS.

A lot of the twitter posts I've found when I searched on Twitter are over the past few months and related to Long Covid, so perhaps this will push forward more recognition and research.

Do you think it's genetic when you and your daughter both have histamine intolerance?

Rhyothemis in reply to Mise

I gathered that the mast cell specialist I took my daughter to sees mostly mastocytosis patients (that's the most well-recognized clonal MCAD, clonal meaning they have too many mast cells). She was very smart and nice, but of course follows the professional association's diagnostic criteria. The doctor I did the phone consult with is actually a neonatologist who herself has Celiac and has recovered from MCAS; the consultation was not really medical advice but informational; I guess that's how it has to be for legal/liability reasons. Also very smart & nice.

I think there is genetic susceptibility; also girls/women seem more susceptible. Sharon Meglathery has a good theory on the genetics (RCCX module theory), but it needs empirical confirmation; I expect that will come eventually. Currently genetic tests will not report on RCCX module variants since MHC class genes are highly variable & variants have not been characterized (they don't know what they do). Here's Meglathery's site:

I wish there was an effort to characterize the proteomics (the type and amount of proteins that are made) that would make a skin biopsy test possible. Maybe there is stuff being done on this. It's hard to keep up with everything.

Another reason for research to be done in this are is that it looks like microgravity (weightlessness) causes MCAS/histamine intolerance in astronauts.

Hi Mise.

Relating to SIBO. This info by Dr Myhill in the UK, any good?


Hi have you actually been diagnosed with anything also are you on the menopause ?

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