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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I have felt so poorly I have done nothing and seen no-one. I speak like Donald Duck, cough like a 40-a-day chain smoker and you can image what massive stress + a virus has done for my M.E. Consequently I really don’t have much to tell you.
