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MCAS and Sleep: How Mast Cells Mediators can Drive Insomnia

Mast Cell Activation Syndrome is the label given to individuals who experience unexplained inflammatory events that are mediated by mast cells and affect several body systems at once. Accordingly, it is often summarized as constant allergy-type symptoms in the absence of an allergen. Histamine is a chemical that mediates the most visible and rapidly-occurring symptoms and, consequently, most of the literature focuses on these manifestations (such as hives, itching and gastric distress). However, many of the MCAS suffers I work with have sleep issues and the mast cell-sleep link remains largely ignored.


Mast cell metabolites

Identifying the locations where mast cells are found in the brain goes some way to understanding how they can impact on sleep, although it is the chemicals that they release from these positions that sets in motion these problems. Mast cells store huge number of chemical mediators in the many granules that can be found throughout the cytoplasm (the liquid space). Under ongoing stimulation from inflammatory signals, these chemicals can be released into the local circulation (either as a classic degranulation event or, depending on the stimuli, the selective release of key mediators). There are many different chemicals released from mast cells, but right now I want to focus on:

Histamine – histamine is one of the most obvious ‘effector’ chemicals in that it induces physiological changes directly (specifically in permeability of local tissues, which is a major issue at the blood brain barrier because of the increased influx of foreign/agitating proteins this can permit). It also increased the glutamate activity at receptors throughout the brain, which is highly relevant in sleep (glutamate is the main excitatory neurotransmitter in our brain excess levels make us ‘wired’). However, it also confers signalling properties, and binds with numerous histamine receptors on microglia; this too stimulates the release of TNF-a, IL-1 and IL-6 which results in further inflammatory activity, including more stimulation of mast cells in a cycle that can become self-perpetuating.

Tryptase – when this binds with microglia in the brain, it stimulates the release of TNF-a, IL-6 and reactive oxygen species, all chemicals that have been shown to increase glutamate through a number of mechanisms (see upcoming article on neuroinflammation). Even on its own, TNF-a is well-characterized as sensitizing our nerves. Although most discussions in this area tend to frame histamine as the main issue, it may well be that tryptase is the biggest deal in sleep disorders; this becomes even more apparent when we consider that, as well as the inflammatory effects described above, tryptase can directly make our brain cells hyperexcitable through changes to the electrical potential of membrane.

There are more chemicals released by mast cells that are relevant here; namely, IL-33 is important due to the way it activates glia (the resident) immune cells of the brain, so too the serotonin (which can be very helpful when delivered to the right areas of the brain, but, when released indiscriminately, can cause issues with permeability of the blood-brain barrier. However, in the interests of avoiding information overload, I have chosen to focus on just histamine and tryptase as the most important concept to understand is the way that mast cells can release these chemicals that a) induce powerful inflammatory changes and b) can result in further activation of other mast cells.




Mast cells and the brain

Despite the lack of attention the topic gets, a bulk of evidence shines light on the strong links between mast cell activation disorder and brain health. While this makes it easier to see how MCAS may drive symptoms in depression and anxiety disorders, it also shines a bright light on the why such strong links exist between these mast cells issues and insomnia. This link becomes staggeringly clear when we consider key brain regions identified for their high mast cell concentration:

  • A driving force in the limbic system, a prehistoric area of the brain that serves to continuously react to changes in our environment and does so without our conscious control, the amygdala is central to the ‘fight and flight’ response. It maintains the ability to hijack our physiology to prepare us for danger (increasing vigilance and increasing heart rate, blood flow to muscles etc) and will do so as soon as it detects any sensory input that has previously been associated with threats. Inflammatory states result in direct over-activation of the amygdala, as well as interfering with calming signals into the structure. While these primary inflammatory impacts on wiring are a problem in themselves, the secondary impact of raised glutamate activity is very relevant in the amygdala as its baseline activity is highly regulated by glutamate/GABA balance.
  • This key structure, also part of the limbic system, can be seen as the link between brain and body. Its main role is to use information provided by key brain centres (such as the amygdala) and, based on this input, to coordinate the appropriate hormonal changes in the body. It has huge impacts on our wellbeing and behaviour through its control of the thyroid, adrenal and gonad axes. Crucially, it is also tasked with regulating sleep and a particular nucleus of the hypothalamus has been described as the ‘sleep switch’.
  • This meninges essentially drip  feed cytokines into the blood entering the brain to ‘raise an alarm’ everywhere this blood may travel . We can see the impact of this clearly in a 2017 experiment, where researchers who applied an inflammatory medium to the meninges saw increased activity in the limbic system (including the amygdala and hypothalamus).


Does everyone with MCAS have sleep problems?

When we examine the mechanisms above, it makes it easy to see why sleep problems are so prevalent in suffers of MCAS. However, possibly the most fascinating thing is that not every mast cell individual experiences insomnia.

What separates these people? It’s sensible to avoid any generalizations, because there are a number of areas of the body and brain that can influence sleep and so it never comes down to just one thing. However, while research already demonstrates the activation state of microglia can predict sleep issues, I fully expect future research to clarify these immune cells as the key route through which mast cells drive insomnia.

So what’s the deal with microglia? The brain’s immune system is different to that seen in the rest of the body and one of the biggest differences is that the brain is equipped with microglia. These cells act in a similar way to macrophages in the rest of the body, performing the role of ‘sentinel’ and initiating a response from the rest of the immune system whenever they flag an issue. Because of the powerful influence they hold in instigating and perpetuating immune activity, their impact on neuroinflammation can be devastating if they become over-activated. Not only do activated microglia produce the excitatory neurotransmitter glutamate, they also produce a number of inflammatory mediators (such as peroxynitrite) that can further push up glutamate levels; this can cause agitation in anyone but can be tragic if neighbouring cells happen to be suffering from a low-energy state, oxygen deprivation or magnesium deficiency (all of which make them super-sensitive to this glutamate and can see them damaged as a consequence, which leads to further inflammation and the initiation of the self-perpetuating peroxynitrite cycle). Stay tuned for my article on neuroinflammation and the peroxynitrite cycle (due to drop late-April 2020… that’s soon).


Treatment: Not Just Mast Cell Stabilizers


You need not look far to find articles praising the benefits of mast cell stabilizers (such as ketitofen or quercetin) in MCAS. Neither is it difficult to find people trialling anti-histamines or employing supplements that help deactivate histamine (which tends to focus on methylation support, such as SAMe). And these are indeed valid strategies; many individuals I work with have noted benefits from using them. However, investigations seem to grind to a halt after these limited considerations and I rarely see individuals turn the corner from these three angles. Equally, several questions remain chronically unexplored:

  • What mast cell triggers is this individual being exposed to? Perhaps it would be better to prevent the initiating event rather than attempt to clean up afterwards?
  • What may be destabilizing the mast cell? If the individual was able to tolerate chemical odours for 25 years, then what changed?
  • What interventions can this person tolerate? Is the MCAS part of a larger sensitivity syndrome?

When it comes to triggers, there can be a range of offenders. As I’ve covered in this article, mast cells can be viewed as ‘the messenger’ in innate immune reactions, and therefore more representative of what this fact-acting branch of the immune system is up against. Chronic infections, dietary chemicals (such as oxalates and lectins), mould exposure, food intolerances (different to allergies) and stress make up the go-to checklist. And I never expect this to be just a singular issues, although one of the above may dominate.

There are also a number of factors that can affect mast cell stability. Systemic antioxidant supply and oxygen delivery play measurable roles, as can magnesium status. The most surprising finding is how alterations in breathing and carbon dioxide can reduce their reactivity and the least surprising is that a lack of sleep make them more likely to react. However, one of the most important factors and one of the most easily measured is porphyrins. These are unwanted proteins formed in excess if there are any blockages in pathway that manufactures heme (needed for haemaglobin and liver enzymes, among many other uses). In summary, this short list contains five different factors that may ‘flick a switch’ in the reactivity of mast cells and, naturally, there are many ways these may be affected by dietary or environmental factors. This further underlies the need for a comprehensive assessment of the metabolism as a whole and personalized treatment strategies (rather than simply introducing an ‘anti-inflammatory diet’).

So let move on to the moment that follows the test results, the case history and a thorough discussion of treatment priorities. It may often be clear what is called for to remedy the situation but there’s just one problem; the individual cannot tolerate it. Inflammation is naturally a definitive part of the MCAS picture but it also inhibits liver enzymes, meaning that we often need to take preliminary steps to ‘make space’ for the treatment that actually does the job; this may be in reducing inflammation through the removal of triggers (as above), binding up endotoxins so that they cannot enter the blood stream so easily or finding other ways to reduce load across the P450 system. This is doubly important in individuals with porphyrin issues, as the hampered heme production may limit the availability of such enzymes, or those with hypothyroidism (as thyroid activity is needed to maintain healthy enzyme activity). Yet again, another time where we are forced to consider the various vicious cycles that characterize.


Because of their central role in inflammation, there are a huge number of potential ways through which mast cells can be triggers. There too exists an array of factors that influence their stability, and so many different things may determine the impact induced by histamine, tryptase and the other products. While this complex interplay makes it difficult to get mast cell-driven sleep issues under control in one go, the positive is that suitable testing/screening always lays out some obvious levers we can pull to elicit improvements.

Leave a comment

  1. Marek, this is exactly what is happening to me and it’s only reading your article have I put the jigsaw together. I am wide awake until about 2pm with histamine flushes and this is because over the lockdown period I’ve eaten high histamine food plus I’ve stopped my probiotics for Kombucha which I’ve felt brilliant on but stupidly didn’t realise it was an high histamine trigger . Dare I ask how to start to lower the histamines ?

    1. The first step will always be to avoid the triggers. This may relate to dietary chemicals, eg. oxalates/lectins/etc, but more often to parasites, other gut issues, mould or an overactive stress response (the latter two are the most potent). Once that is done, there is rarely more work to do but there will be times when copper status and methylation activity will be a big help, and on rare occasions some more tactical immunomodulatory steps.

    2. Me too. Also I got covid, which aggravated my MCAS by a hundred percent.

  2. I have been diagnosed with MTHFR, Hashimotos, histamine intolerance and have horrible insomnia! I feel fine during the day, but suffer horribly at night. I’ve looked for a solution for 30 years. Its incredible that I’m still here…

    1. Sorry to hear you have been suffering. I see regular links between the histamine issues and insomnia. It seems important that the immune activity is higher at night, although I would always be keen to measure adrenal activity too (as the primary factor controlling sleep/wake cycles and daily rhythms). An Adrenal Stress Profile (salivary test) is a good place to start. Hope that helps.

    2. Hi Barb, I have the same problem. I haven’t slept more than 2-4 hours in over 20 years. I have the worst osteoporosis the doctors have ever seen in someone my age (60). They usually see this in someone in their late 90’s. I function on high histamine all day. Sleep for a few hours and then do it again, but it definitely ages the body much faster than normal on many levels. I hope you have found a solution to your insomnia, I am still searching………

    3. Hello,
      Thank you for writing and posting this article. It has given me a bit of hope, relating to the anxiety and sleep issues I have, that have been largely ignored or misdiagnosed through the many doctors I have seen over the years.
      Your mention of chemical triggers is very comforting and encouraging.
      I am a 52 y/o post menopausal woman that was diagnosed with MCAS last year, after years of misdiagnosis and debilitating symptoms. I quit smoking a year and a half ago using a Juul device and that is when my symptoms exploded. Throat swelling, whole body numbness, pounding heart with fast heart rate, vision disturbance and severe anxiety with sweating were the most prevalent symptoms. All but the numbness I had been experiencing for years to a lesser degree.
      I was sent to a neurologist, an endocrinologist, a rheumatologist, a cardiologist and a psychiatrist. After testing, all were at a loss. Then on my own decided to visit an allergist who knew right away what was wrong. Tested my Tryptase levels and diagnosed me with MCAS.
      Sadly, he retired just after diagnosis. He prescribed, Accolate and off brand antihistamines that did not contain propylene glycol, (the Juul ingredient) recognizing this as a trigger and referred me to another (very young, and arrogant) doctor (he did not know) who called herself an MCAS specialist. Right out of the gate she stated, “I’m not sure you have MCAS”, prescribed H1 and H2 blockers that contain propylene glycol and other chemicals that I’m certain cause a reaction.
      She stated that I should just ignore the ingredients, that they aren’t likely contributing to my symptoms.
      When I explained my hesitancy she became agitated and demanded that I try, saying that I’m “fixated” on chemicals and that chemicals don’t cause MCAS symptoms. She also stated that anxiety followed by sweating with sleep disturbance isn’t a symptom. That last visit with her left me in tears and hopelessly doubting my MCAS diagnosis, thinking maybe its all in my head and the diagnosis was in fact wrong.
      Anxiety, flushing, sweating, pounding heart and sleep issues -chills followed by severe anxiety, fast heart rate and then sweating when falling asleep- is my most debilitating symptom.
      Throat swelling, sinus, blurred vision, headaches and gastrointestinal symptoms after eating are second to the sleep difficulties.
      I am at loss with finding a doctor who properly understands and treats MCAS in my area,Tampa Florida. My life has been upended and I am at my wits end.
      I am hoping you may be able to provide me with some advice and are able recommend a physician in my area.
      Thank you for your time and again for this post.
      Elizabeth B.

      1. What else should I say other than I feel you. I am in the same boat. I hope you find some peace!

      2. I know this is from 3 years ago, and I hope you have found help since, but just in case, let me just say: That doctor is wrong! Very wrong. You sound like you have MCAS, and chemicals, especially propylene glycol, DO DEFINITELY effect mast cells. That chemical is used in antifreeze and is toxic even to healthy people. Please don’t let her make you doubt yourself. If you are in Florida, you are probably exposed to mold and fungi on a daily basis. These are huge mast cell triggers. The propylene glycol, or even Covid exposure without you knowing it, might have just pushed your already irritated mast cells over the edge. Go to and search in the search bar Mold Detoxing. I have been diagnosed with MCAS and with its related conditions, Ehlers Danlos Syndrome and POTS/Dysautonomia. You might have these other conditions yourself. Either way, you can go to, look up a doctor in your area. Even if you don’t have EDS, the doctors on that site often are very knowledgeable in MCAS and can help you. I’m on the west coast so I only know doctors here. Also, if you have any doctor that can help you in the meantime, see if they can prescribe you Ketotifen (1mg starting dose, work up to 2mg twice a day) and Cyproheptadine as needed (4mg is the usual starting dose, can go up to 8mg three times a day safely). They are great antihistamines. They are worth discussing with a doctor who is willing to help you try something. Of, course discuss any other supplements or meds you are on to make sure you can take them safely. They worked for me. Cyproheptadine helps me with the attacks I get similar to yours (chills, tremors, nausea, severe anxiety/panic, increased heart rate, pounding pulse, muscle spasms, etc.). Hope this helps! Don’t give up! It’ll get better. It just takes time and patience. You will have steps forward and steps back, but overall you can get better, if you haven’t already.

  3. Thanks for your awesome post. I have no symptoms other than insomnia and as dreaming within circles repeating everything.
    Histamine-related. But l-glutamine, hydrolized collagen and whey are the strongest triggers.

    After trying everything under the sun, I do not see how to counteract the peaks. Why glutamine (to glutamate) is in the loop together with histamine?
    I tried with gaba when the symptoms appear at midnight but no result, however bezos work but I do not want to use them?
    What to try to lower that unbalance glutamate/histamine?

    1. First, its important to note that glutamate and histamine are two separate pathways that intertwine in neuroinflammation. Also that we’d only expect Glutamine to have this pro-glutamate effect when it reaches the brain in excessive amounts (gut barrier? blood/brain barrier?) or when it does not get converted to GABA effectively (low B6? uncontrolled inflammation?) or can accumulate too easily (low DHEA? low magnesium/manganese?), so these are areas worth looking into. Because of the size of the molecule (which is too big the cross the blood/brain barrier), supplemental GABA should not actually work; if people do or do not, this can provide information on the state of the blain/brain barrier (and thus, whether you should look into other areas first). Hydrolyzed collagen is something that offers lots of benefits but I’ve seen conventionally-sourced products cause problems in those with glyphosate issues (glycine/glyphosate interaction?). Whey is not something I see many intolerances to (but they do still occur) but there’s also something to be said for the effects in the gut (biofilms? interactions with sulphate-reducing bacteria?) and metabolic reactions involving cysteine.

      In short, there’s not one answer to your question…

    2. Please may I ask you to elaborate your sleep circles and if you’ve found anything that works? I’ve had chronic insomnia for 20 years and repeatedly get ‘stuck’ in incredibly repetitive dream states. I’m reliant on amitriptyline and Zolpidem which I need to come off, but without them this is what happens. I also have tightening of muscles in my chest which only slowly wears off throughout the day and experience buzzing, which at it’s worst is like powerful vibrations that move in waves through my whole body. It kind of grips me from the inside, my heart pounds and I have loud ringing like a bell or pneumatic drill in my head. I have ME, POTS, fibromyalgia, and have episodes of flushing and chills. I don’t know the cause, but I think it may be connected to cleaning products and chemicals such as paint.

      1. Hi May, when it comes to dealing with insomnia that is driven my mast cells issues, the key has always been to determine which pathways are driving the mast cell issues in the first instance (I’ve got a chart on which shows the most common factors). If you haven’t had an Organic Acids test, I would recommend doing so; this can help determine which of these pathways may be key in YOUR case. Equally, it would provide information on your dopamine status; whenever I see people experience the patterns of muscular tension (when you remove the medications), it has often been connected to dopamine (although magnesium status and general ATP availability are the other usual suspects).

  4. Thanks for the great article. I was diagnosed with Alpha Gal Syndrome last Fall and really have slept very little over the past few months. I am taking Ketotifen and Zafirlukast plus Zyrtec, all twice daily. I think that mix helps (as in the nights are not complete horror shows, but they are still pretty bad.). I have been using an Apple Watch that keeps me sane by being able to see exactly how awful my sleep is.

    1. Its clear that, in these situations, any improvement is a welcome improvement… but I hope the connections laid out here give you a good starting point in getting further gains!

  5. Wow, another very informed post!

    No one I’ve consulted with knows much about porphyrins. I plan to have another test shortly as at least I was able to convince my provider to do another for me.

  6. Hello,
    Could diarrhea and insomnia be the only symptoms of MCAS?

    1. Yes, that is entirely possible. Normally we’d expect a more extensive list, but I have worked with individuals for whom their only reported symptom was insomnia…

  7. I am testing porphyrins in urine. Should I wait until I am having a big reaction to test, or can I test between reactions?

    1. There are no right-or-wrongs but it can be easy to miss porphyrin patterns when the test is taken on a ‘good’ day. By default, I would tend to wait for flare-ups to get the most detailed picture (as what I am most keen to establish is what is going on when these issues are most problematic).

  8. I found something new that works incredibly well and I want to share it with you. This bracelet works! Now I feel very healthy and comfortable. My sleep problem is gone.

  9. Hello! I can not find a doctor that is familiar with this. I had covid with debilitating symptoms after. After all my research I was drawn to MCAS. I started the Zyrtec and pepcid protocol. 2 times daily. I significantly improved. Followed with a low histamine diet. But I’m still so fatigued. Brain fog. Vision disturbances. Any recommendations?

  10. Had covid January 2021 haven’t slept natural since. On H1 and H2 blockers twice a day. Low dose invermecin. Been told to try LDN. So worried about filling my body full of chemicals. I’m in the UK pleas please direct me to someone who can help. It’s a mind field. Thank you

  11. Hi, Marek!
    First of all a MASSIVE thanks for all your work. This site gives so much life-saving info and hope. I would have a million questions, but I’m gonna keep it simple and focus on the part where you said that CO2 and breathing were used to mitigate the problem. The study showed that CO2 decreased MC granulation… But it was done with exogenous CO2, right? But what does it practically mean for the breathing? That you should breath so that your CO2 is elevated (slow and deep / breath holds) or the opposite?
    Also in some other article you mentioned that your patients have had positive effects from Holotropic breathing… I’ve stopped doing Wim Hof-, holotropic- and other hypoxia inducing-breathworks when I got sick, because I felt that the hypoxia triggered a collapse. Should I try to incorporate them back into my progress and trust that those collapses were, in fact, due to something else (or maybe Herx-reaction, or something?)?
    Thanks a million to you!

    – Rauno

    1. I ask my self the same.
      What I know is that Wim Hof breathing has much to do with activating a adrenalin reaction which in my hyperarrousal states and stress problems I better avoid. I guess my adrenal glands are already working a lot.
      Let me know if you got an answer

      1. Wim Hof breathing is a powerful tool… for some. The only hesitation I have with this style of breathwork is that it is a little one-size-fits-all (and, as you mention, many individuals will not do so well with the sympathetic activation that will occur from this breathing pattern). This gets into the world of regulating BOTH the sympathetic and parasympathetic activity, which is necessary in order to elicit the benefits of breathwork (and there are some massive benefits here), and this is why most people will do best through arranging some guided breathwork with a practitioner; this allows for someone to not only check for (and provide remedial steps for) restrictions in breathing patterns but also to observe for responses in the central nervous system and modify the breathing rhythms on a live basis. Doing so allows for enhancing sympathetic activity when we want to help bring sensory signals to awareness, while promoting parasympathetic activity to stabilize the system as required. This is where individuals tend to go from a place ‘breathwork sounds good, but it only works for me some of the time’ to having a powerful tool that they can use to reliably regulate their nervous system (and sees them report that they can now reliably access the benefits in solo sessions too, something that may have been highly inconsistent previously). I most often recommend that individuals contact practitioners of Transformational Breathwork and Conscious Connected Breathwork (although I also see some great results from those engaging in Holotropic Breathwork too).

    2. I would say your are closer to the studie with the co2 when you are breathing into bag instead of wh.

    3. CO2 is going to have the same effects on mast cells whether this originated from cellular metabolism or was taken up through the lungs. The key to CO2 management has always been to ‘train’ (or detrain, to be more accurate) the chemoreceptors that regulate our responses to increases in CO2 concentration. If we spend years shallow/fast breathing, we push out more CO2 and these receptors can get adjusted to low CO2. They then panic when CO2 levels start to rise (even if this is going from ‘low’ to ‘moderately low’) and so we never have a fair chance of maintaining a higher/more desirable level of CO2. This is where approaches like Buteyko breathing and that described by Patrick McKeown in The Oxygen Advantage can be helpful… even just deliberate nose-breathing (and mouth-taping at night) can be a good start here. However, its also worth pointing out that many people will have physical restrictions in their breathing that a breathwork practitioner that may stop them from benefitting (a breathwork practitioner can easily spot this and help correct it), or just a big activation of the sympathetic stress response that overrides these efforts at ‘retraining’ the system (and for which a tailored blend of nutrition, lifestyle, sleep, somatic/breathwork/processing work are going to be called for).

      Whenever people notice any collapse from breathwork (or any advanced introspection/meditation techniques), it is almost always because the process has allowed more sensory signals to reach awareness than you have the resources to handle. This is where the human nervous system is designed to ‘freeze’ (aka hibernate, or play dead) until a) the threat passes or b) we gain more resources. This is where contacting a breathwork practitioner to arrange a guided session can be very helpful (most specifically in regards to having someone guide your breath patterns in a tailored manner, activating the sympathetic response with the in-breath when desired and the parasympathetic response with the out-breath as required). But also the amount of resources available at baseline have a big role in whether the nervous system will deploy this type of shutdown, and so its fruitful to investigate energy production (mitochondrial performance), energy signalling (insulin/thyroid/etc) and energy theft (from excess immune activity). The Organic Acids Test is a good place to start.

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