MCAD v HIT

I’ve noticed that whenever I talk about histamine and food here on my blog there is often confusion about the cause of food reactions, so I thought I’d write down my take on what’s happening.  I’m no expert, though, just a patient along with the rest of you so I could be well off the mark and I’m sure if I am someone will point it out 😉 .

I’ve had MCAD my whole life, but I have never reacted to foods.  I don’t have a nut allergy, or a gluten allergy, for example and have always been able to eat whatever I like.  I know I’m extremely lucky and many of my readers aren’t so fortunate.

I only started reacting to food when I was in my mid forties.  It came on gradually over a few years.  Bright red flushing after meals, increasingly itchy skin, hives which I’d never had before and out-of-control acid reflux.  Eventually in 2013 all hell broke loose and I started having anaphylactic reactions after I ate anything – severe palpitations, muscle spasms (particularly in my gut and back), weird head rushes that felt like I was having a stroke, anxiety (obviously the whole situation made me anxious, but the adrenalin fuelled anxiety from anaphylaxis is a different thing altogether), huge spikes then huge crashes in blood pressure, and eventually I’d just pass out.  It was terrifying and I had absolutely no clue what was going on.

To cut a very long story short I paid to see Dr Seneviratne at St Mary’s, who tested my DAO levels which were well below normal and he diagnosed me with Histamine Intolerance (HIT).  I’d never heard of the disease before so it was a steep learning curve!   Most foods contain small levels of histamine but some foods contain large amounts.  I don’t eat meat, and it turns out that many of the staple vegetarian foods I was eating every day (cheese, tinned tomatoes, soya beans, spinach, aubergiene) are all high in histamine :-/  Our bodies also produce histamine as part of the digestive process which is why I could react some days after drinking just water!   Fortunately we have a couple of enzymes in our bodes, DAO and HNMT, which ‘mop up’ the histamine we ingest so that it doesn’t cause us any problems.  For people with HIT, however, the enzymes are low or not working correctly so the histamine we eat in foods, and the histamine produced from digestion, accumulate in our bodies.  It’s a bucket effect – the more histamine we eat the more it builds up, and eventually the bucket overfills and we have a reaction.  No one specific food does this – it’s a cumulative effect.  I embarked on a low histamine diet and within 4 months my food reactions were under control – they hadn’t gone, but they were manageable.

There are various reasons why, if we suffer from Histamine Intolerance, our DAO and/or HNMT levels could be low.  For example, they can be reduced by taking certain medications, in which case if you cease taking the drugs the enzymes should return to normal and the HIT would only be temporary.  In my case, however, I have no idea why my DAO isn’t as it should be – I wasn’t on any drugs, my diet was very healthy and I hadn’t had any major tummy bugs or infections.  For me, HIT seems to be a permanent problem and if I veer off my low histamine diet the anaphylactic reactions come back within a couple of weeks 😦

Because histamine build-up in HIT is a bucket effect, I can often have no problems eating my breakfast in the morning but I can quite often react to my dinner in the evening, because histamine has accumulated during the day.  So I tend to eat my main meal at lunchtime and just have a small snack at night.

The food issues faced by HIT patients are very different to the food issues faced by many Mast Cell Disease patients.  In MCAD the immune system is treating totally normal foods as a foreign invader and mounting a defence against them.  It could be any food and will differ from patient to patient.   It is not a build-up and the reaction comes on soon after the food is eaten (although some people do have mild, delayed reactions which muddies the waters!).  In MCAD our mast cells release chemicals including, but not limited to, histamine which then gives us an allergic-type reaction.   Our immune system doesn’t care whether the food is high in histamine or not – it can react to any food it likes which makes treating MCAD food reactions much harder than treating HIT food reactions!   For some people with MCAD the immune system is so over-reactive they are left with only a handful of foods that are ‘safe’ 😦

It’s important to note that in MCAD the immune system doesn’t just react to food – our mast cells can react adversely to just about anything in our environment.  My biggest reactions are to drugs – my mast cells hate them – but I also react to stress, hormones, some smells, pollen, my dog and often my own emotions.

The biggest difference between HIT and MCAD, is that HIT is a food issue only Stop eating high histamine foods and it is possible to get your HIT under control.  In MCAD the issue is much, much wider and not eating high histamine foods won’t alter the fact your mast cells react to hairspray, the smell of bleach or your hamster.

MCAD and HIT are totally distinct and separate illnesses – you can have HIT without having MCAD, and MCAD without having HIT.  However, if you’re unlucky enough to have both they can definitely affect each other and I think that’s where much of the confusion around food comes from.  I have people comment on my blog that they are following a low histamine diet but still reacting to all sorts of foods and of course they will if they suffer from mast cell disease.  Following a low histamine diet will only stop reactions after eating if you suffer solely from HIT.  It might reduce your symptoms if you have MCAD, because if your body is already over-whelmed by histamine adding to the load by eating lots of food high in histamine probably won’t help the situation, but a low histamine diet most definitely won’t cure all your symptoms which are caused by factors other than food.  At least that’s been mine and my friends’ experience.  So it’s important to know whether you’re suffering from HIT, MCAD or a combination of the two because management strategies will be very different, and you can only know this if you are tested by someone knowledgeable in both diseases (easier said than done I know, especially in the UK).

As far as I know there is no data available on whether HIT is more common in the mast cell disease population.  It would be interesting to know if there’s a link, because every piece of the puzzle is important when we’re trying to work out what causes disease and how to treat it.

 

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15 thoughts on “MCAD v HIT

  1. melody

    Thanks, Jak. I’m always happy to see an email notice in my inbox that you’ve written another post and this one is very helpful for me. I want to tell you that you have an amazing way of clarifying and cutting through bullshit and I’m grateful for all the information you provide.

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  2. Jan Groh

    I can’t speak to HIT (I’m not diagnosed with it), but… I now believe most of my food reactions (which are all relatively low, and slow and not true IgE driven allergies) are all IgG driven so-called “sensitivities” as I think I now have a very leaky gut at 52. Mine started acting up in my 40’s, with age and probably increased leakiness. I do fare better on a low-histamine diet. (I miss a good aged cheese the most.) An ND (naturopathic doctor here in the US) helped me to uncover this with a test for same in 2012.

    I think several factors play into this for me as an hEDS now HHSD patient: weak epipthelial layers from the hEDS/HSD (mine is clearly genetic if you look at my family), plus eating loads of gluten before (some NDs feel this lends to leakiness), and I think MCAS itself. (Some other doctors say this can lead to leaky gut.) So, while I don’t seem to have what you describe as an immediate MCAS reactions, I definitely have a reaction to almost everything I eat, but especially everything I eat the *most*, which is tell-tale for IgG sensitivity.

    The only way I can explain my sensitivity to sunlight, vibration, stress (strong emotion), chlorine, fluoride and temperature is with MCAS though. So who knows exactly what’s driving? And yes, someone could have all 3 or more. Whee. I’m about to go back on the GAPS diet again to give my gut a break again. (Did in 2013, and “came to Jesus” about my diet after that. It was brilliant for me.) I do best on a GFDF ketogenic diet with some paleo breaks myself. But that’s just me.

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    1. Melanie Odell

      There is another disease out there to which could explain the chlorine, fluoride sensitivities etc. MCS. Simply called Multiple Chemical Sensitivity Syndrome. You could try researching it for yourself and see if it maybe it’s symptoms might feel familiar to you and go from there.

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      1. Jan Groh

        Oh I know. but I now think MCAS is the actual driver of it, at least in myself. (I.e, the other way around.) I’ve known about MCS for 30 years. Else, they are highly comorbid. Dogs don’t bark for no reason, neither do our mast cells…

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      2. melody

        I’ve often wondered, is Multiple Chemical Sensitivity a subset of mast cell issues? I have pretty severe MCS, but also have things like cold urticaria, hypermobility, etc., which has led me to think my MCS is basically part of MCAS and if I do have something like hEDS, then maybe both are related to that.

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        1. Jan Groh

          This is the $64K Question for all of us. Hopefully science will catch up in time. I strongly suspect this is the case, but no, can’t say with 100% certainty. But I think MCS and Fibro are just the best diagnoses they could come up with in the past for what we now recognize and I think are most likely variations of hypermobility spectrum disorders and MCAS in most. I’ll just say this much, I have yet to meet a fibro patient with MCS who doesn’t show signs of a hypermobility spectrum disorder as well. (I used to run the Brighton with an “r” dx criteria on them backwards – leaving the 9pt Beighton scale for last. All of them passed, and almost all of them also passed the Beighton scale at the end too. Yes, I know this is now obsolete since 2017. Just illustrating past experience.) I write at length about all of this on my blog.

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        2. Melanie Odell

          I actually wondered if MCS is really just an early name for Mast Cell actually myself. They certainly seem to be related at any rate. Unless MCS as as you said is subset of Mast Cell with no digestive involvement.

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          1. Jak Post author

            Because my worst reactions are to drugs and I didn’t react to foods, I was initially diagnosed as having MCS at the regional allergy centre before this was changed to MCAD. I personally think MCS is MCAD, but of course I could be wrong.

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    2. Melanie Odell

      In my personal experience with Mast Cell Disease my immediate reactions are to the environment, especially pungent chemical odors, but my food reactions are slow, they set in at two hours on the dot, and continue in various forms of symptoms for 5 to 7 days. Currently I react to all food except peas, beef and chia seed oil, and water. That is all I am able to consume without fairly violent post ingestion reactions. The fact that your food reactions are not immediate does not steer away from a mast cell disorder at all. Stress of course plays a huge role in mast cell disorders. Well in most diceases of course, but the problem with a Mast Cell Disorder is, if it is severe, we can react to anything, at any time, so that fear factor is an always hovering presence. That is very stressful. With most other diseases you can practice avoidance, but with Mast Cell it can be almost impossible to do that with any effectiveness. It makes keeping stress at bay, a real and constant struggle.

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      1. Jak Post author

        Couldn’t agree more Melanie. The fear of living with MCAD and not knowing from one day to the next what you will react to is soooooo scary and incredibly stressful. I find the whole emotional side of MCAD exhausting 😦

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    3. Jak Post author

      I miss cheese too Jan – OMG what I would give for melted cheddar on toast *drool*.

      For some patients there is definitely a mish mash of conditions going on. Must be so difficult to separate them all and I feel for you.

      I’m lucky (I guess!) that my worst mast cell reactions are to drugs and they happen within 20-30 minutes of ingestion. I’ve also had severe reactions to physical stimulation (osteopathy, acupuncture etc.) and again they are fairly immediate. Must be really hard if the reactions come on hours later to try and work out what the trigger was.

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  3. Karen, The Walking Allergy

    Well written, Jak. I most definitely do not have HIT, and some high histamine foods get me, some don’t. Anything that has a hint of mold (aged cheese, salami, fermented stuff like kombucha, etc) is a guaranteed nightmare, but a lot of those foods are also high in histamine, to add to the logic puzzle. I have IgG reactions, like Jan, add in my special IgE reactions as well, that makes me the ridiculously reactive person I am. Not a lot of Masties anaphylax from dust, dogs, cats, etc. I think that the level of severity of your, Jan’s, my MCAS comes from having those ‘add ons’ to MCAS. They take MCAS to the next level, I think. I also know that researchers are even now still finding new mediators released by mast cells, there’s more that we don’t know than what we do know, ya know? 😉

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