Cardiovascular manifestations of mast cell disease: Part 3 of 5

Recurrent or perpetual elevation in blood pressure has been observed in multiple studies and may affect up to 31% of patients with mast cell activation disease (systemic mastocytosis, mast cell activation syndrome/disorder, monoclonal mast cell activation syndrome). Despite this high prevalence, many providers continue to believe that this symptom cannot be inherently from mast cell activation.

A number of mast cell mediators are vasoconstrictors, narrowing the blood vessels and elevating blood pressure. Histamine can both increase and lower blood pressure depending on which receptor it acts upon (H1: hypotension; H2: hypertension).

Several mediators participate in the angiotensin-renin pathway. Angiotensin II, the level of which is largely determined by mast cell mediators like renin, strongly elevates blood pressure. Chymase, involved in the angiotensin-renin pathway, can also either increase or lower blood pressure depending on concentration relative to other mediators present. Carboxypeptidase A can also affect angiotensin II level as well. Renin regulates the level of a molecule that becomes angiotensin II and can increase blood pressure this way.

Phospholipases, which help produce the molecule needed to make prostaglandins, leukotrienes and thromboxanes can contribute to either high or low blood pressure depending upon which molecule is made. Prostaglandin D2 (PGD2) is a vasodilator, lowering blood pressure; but its metabolite, 9a,11b-PGF2, increases blood pressure. (Author’s note: I personally believe this to be the reason for the rapid blood pressure fluctuations in mast cell patients, but do not have evidence to directly support this.) Thromboxane A2, a molecule related to prostaglandins and leukotrienes, increases blood pressure, as do leukotrienes.

Management of high blood pressure is complicated in mast cell patients by the interaction of common antihypertensives with mast cell activation. Beta blockers are contraindicated in mast cell patients because they interfere with epinephrine, both naturally produced and medicinally.  Use of beta blockers is a risk factor for fatal anaphylaxis.  Any patient on beta blockers that carries an epipen should also carry a glucagon pen, which can be administered prior to the epipen to increase efficacy.

ACE inhibitors interfere with angiotensin converting enzyme, which increases blood pressure through the angiotensin II pathway.  ACE inhibitors affect bradykinin levels, a mast cell mediator that is also mast cell activating.  For this reason, ACE inhibitors can increase mast cell reactivity and symptoms like angioedema.

Author’s note:  I extended this series to four posts to discuss heart failure in mast cell patients.  Following this series, I will be posting a series dedicated exclusively to Kounis Syndrome, including diagnosis and treatment.  Sit tight!

References:

Kolck UW, et al. Cardiovascular symptoms in patients with systemic mast cell activation disease. Translation Research 2016; x:1-10.

Gonzalez-de-Olano D, et al. Mast cell-related disorders presenting with Kounis Syndrome. International Journal of Cardiology 2012: 161(1): 56-58.

Kennedy S, et al. Mast cells and vascular diseases. Pharmacology & Therapeutics 2013; 138: 53-65.

 

Cardiovascular manifestations of mast cell disease (Part 2 of 5)

Abnormalities of heart rate and rhythm can occur due to action of several mast cell mediators. Histamine binds at histamine receptors numbered in the order of identification: H1, H2, H3 and H4. Histamine binding at H1 receptors on cardiomyocytes (heart muscle cells) slows the heart rate, while histamine binding at H2 receptors increasing heart rate and the force of heart contraction.

As I mentioned in the previous post, histamine binding at the H3 receptor decreases the release of norepinephrine. Another mast cell product, renin, modulates angiotensin II, which can increase norepinephrine release.  Increased levels of norepinephrine triggers increases in heart rate and force of contraction.  This means that whether or not mast cell activation causes tachycardia depends largely on how much renin and histamine are released. Much less histamine is necessary to trigger the H3 inhibition of norepinephrine release relative to the amount needed to affect heart rate through H1 and H2 receptors.

Prostaglandin D2, a mast cell mediator, can also cause tachycardia.  Of note, prostaglandin D2 is not stored in mast cell granules.  It is made following mast cell activation and is considered part of the “late phase allergy response”, which can occur several hours after exposure to a trigger.

Tachycardia is a common symptom for mast cell patients.  The recommendation in a recent review article is to treat when the heart rate is perpetually over 100-120 bpm, or when it is extremely distressing to the patient. There are a number of options for treatment. As it can be caused directly by mast cell behavior, mast cell medications such as antihistamines (H1 and H2) should be adjusted for maximum effect. Renin inhibitors, such as aliskiren (Tekturna in the US), can be used to treat supraventricular tachycardia (SVT) in mast cell patients, as can angiotensin receptor blockers like losartan, valsartan and others. Patients on renin inhibitors or angiotensin receptor blockers can also decrease blood pressure.

Calcium channel blockers, like verapamil, are also an option.  The medication ivabradine treats tachycardia in patients who have a regular heart rhythm and does not affect blood pressure.  Ivabradine is not used to treat atrial fibrillation. β-blockers are contraindicated in mast cell patients because it interferes with the action of epinephrine, making patients more likely to have reactions and epinephrine less likely to treat effectively.

References:

Kolck UW, et al. Cardiovascular symptoms in patients with systemic mast cell activation disease. Translation Research 2016; x:1-10.

Gonzalez-de-Olano D, et al. Mast cell-related disorders presenting with Kounis Syndrome. International Journal of Cardiology 2012: 161(1): 56-58.

Kennedy S, et al. Mast cells and vascular diseases. Pharmacology & Therapeutics 2013; 138: 53-65.

Cardiovascular manifestations of mast cell disease (Part 1 of 5)

Mast cells are present in the cardiovascular system under normal conditions both in the heart and near vasculature, often in spaces close to nerve endings.  They perform a variety of necessary functions including participating in the pathway to generate the hormone angiotensin II, which encourages an increase in blood pressure.  Mast cells in the heart and vasculature are usually positive for both chymase and tryptase in granules. Mast cells in the cardiovascular system have also been tied to a number of conditions, including atherosclerosis, arrhythmias and aneurysm.

Mast cell patients may experience a number of cardiovascular symptoms or events. 29% of SM patients and at least 20% of MCAS patients report palpitations and supraventricular tachycardia.  31% of patients with mast cell activation disease (MCAS, MMAS, SM) experience episodic or chronic elevation in arterial blood pressure due to mast cell activation. Ventricular fibrillation, cardiac arrest and Kounis Syndrome can occur in mast cell patients due to mast cell activation.  Few cases of heart failure in SM patients have been reported.

Kounis Syndrome is an acute coronary syndrome provoked by mast cell mediator release. In one series, ten mast cell patients (5 MCAS, 3 MMAS, 2 ISM) suffered acute coronary syndromes.  These patients reported “oppressive” chest pain of the type commonly seen in ischemic cardiac events.  The triggers for these events were diverse: venom immunotherapy, mepivacaine, exercise, penicillin, general anesthesia, wasp sting, metamizole and moxifloxacin.  In seven patients, the echocardiogram was normal.  In the remaining, left ventricular hypertrophy, anteroseptal hypokinesia, medioapical hypokinesia, inferoseptal akinesis, lateral apical akinesia and left ventricular ejection fraction of 40% were found on echo. Only six patients had elevation of troponin, a test commonly used to diagnose heart attack and acute coronary syndromes.

Mast cell mediators exhibit a wide range of effects on the cardiovascular and nervous systems. Mast cell mediators can affect release of norepinephrine by sympathetic nervous system, contributing to arrhythmias.  In some instances, release of norepinephrine has been linked to sudden cardiac death, although not linked specifically to mast cell patients. Histamine actually decreases norepinephrine release by binding to H3 receptors on nerve endings.

As mentioned above, mast cells participate in modulating the level of angiotensin II. Mast cells release renin, which leads to the formation of angiotensin II. Angiotensin II then binds to AT1 receptors on sympathetic nerve endings, raising blood pressure. Angiotensin II can also cause arrhythmias without involving the nervous system.

References:

Kolck UW, et al. Cardiovascular symptoms in patients with systemic mast cell activation disease. Translation Research 2016; x:1-10.

Gonzalez-de-Olano D, et al. Mast cell-related disorders presenting with Kounis Syndrome. International Journal of Cardiology 2012: 161(1): 56-58.

Kennedy S, et al. Mast cells and vascular diseases. Pharmacology & Therapeurics 2013; 138: 53-65.

Master table of stored mast cell mediators

Mediator Symptoms Pathophysiology
Angiogenin Tissue damage Formation of new blood vessels, degradation of basement membrane and local matrix
Arylsulfatases Breaks down molecules to produce building blocks for nerve and muscle cells
Bradykinin Angioedema, swelling of airway, swelling of GI tract, inflammation, pain, hypotension Vasodilation, induces release of nitric oxide and prostacyclin
Carboxypeptidase A Muscle damage Tissue remodeling
Cathepsin G Pain, muscle damage Converts angiotensin I to II, activates TGF-b, muscle damage, pain, fibrosis, activates platelets, vasodilation
Chondroitin sulfate Cartilage synthesis
Chymase Cardiac arrhythmia, hypertension, myocardial infarction Tissue remodeling, conversion of angiotensin I to II, cleaves lipoproteins, activates TGF-b, tissue damage, pain, fibrosis
Corticotropin-releasing hormone Dysregulation has wide reaching and severe effects Stimulates secretion of ACTH to form cortisol and steroids
Endorphins Numbness Pain relief
Endothelin Hypertension, cardiac hypertrophy, type II diabetes, Hirschsprung disease Vasoconstriction
Eotaxin (CCL11) Cognitive deficits Attracts eosinophils, decreases nerve growth
Heparin Hematoma formation, bruising, prolonged bleeding post-biopsy, gum bleeding, epistaxis, GI bleed, conjunctival bleeding, bleeding ulcers Cofactor for nerve growth factor, anticoagulant, prevents platelet aggregation, angiogenesis
Histamine Headache, hypotension, pruritis, urticaria, angioedema, diarrhea, anaphylaxis Vasodilation of vessels, vasoconstriction of atherosclerotic coronary arteries, action of endothelium, formation of new blood vessels cell proliferation, pain
Hyaluronic acid Degradation contributes to skin damage Tissue repair, cartilage synthesis, activation of white blood cells
IL-8 (CXCL8) Mast cell degranulation Attracts white blood cells (mostly neutrophils) to site of infection, activates mast cells, promotes degranulation
Kininogenases Angioedema, pain, low blood pressure Synthesis of bradykinin
Leptin Obesity Regulates food intake
Matrix metalloproteinases Irregular menses (MMP-2) Tissue damage, modification of cytokines and chemokines (modifies molecules to make them useful)
MCP-1 (CCL2) Nerve pain Attracts white blood cells to site of injury or infection, neuroinflammation, infiltration of monocytes (seen in some autoimmune diseases)
MCP-3 (CCL7) Increases activity of white blood cells in inflamed spaces
MCP-4 (CCL13) Shortness of breath, tightness of airway, cough Attracts white blood cells to inflamed spaces, induces mast cell release of TNFa and IL-1, asthma symptoms
Phospholipase A2 Vascular inflammation, acute coronary syndrome Generates precursor molecule for prostaglandins and leukotrienes
RANTES (CCL5) Osteoarthritis Attracts white cells to inflamed spaces, causes proliferation of some white cells
Renin Cardiac arrhythmias, myocardial infarction, blood pressure abnormalities Angiotensin synthesis, controls volume of blood plasma,lymph and interstitial fluid, regulates blood pressure
Serotonin/5-HT Nausea, vomiting, diarrhea, headache, GI pain Vasoconstriction, pain
Somatostatin Low stomach acid symptoms, low blood sugar Regulates endocrine system, cell growth and nerve signals, inhibits release of glucagon and insulin, decreases release of gastrin, secretin and histamine
Substance P Neurologic pain, inflammation, nausea, vomiting, mood disorders, anxiety Transmits sensory nerve signals, including pain, mood disorders, stress perception, nerve growth and respiration
Tissue plasminogen activator Blood clots Activates plasminogen, clotting
Tryptase Hematoma formation, bruising, prolonged bleeding post-biopsy, gum bleeding, epistaxis, GI bleed, conjunctival bleeding, bleeding ulcers; inflammation Activation of endothelium, triggers smooth muscle proliferation, activates degradation of fibrinogen, activates MMP molecules,tissue damage, activation of PAR, inflammation, pain
Urocortin Increased appetite when stressed, inflammation, low blood pressure Vasodilation, increases coronary blood flow
Vasoactive intestinal peptide Decreased absorption, low blood pressure, low stomach acid symptoms Vasodilation, mast cell activation, lowers blood pressure, relaxes muscles of trachea, stomach and gall bladder, inhibits gastric acid secretion, inhibits absorption
VEGF Diseases of blood vessels Formation of new blood vessels, vasodilation and permeability of smaller vessels

Exercise and mast cell activity

Research on exercise induced bronchoconstriction represents a large body of work through which we can draw conclusions about mast cell behavior as affected by exercise.

Exercise has been found in a number of studies to induce mast cell degranulation and release of de novo (newly made) mediators. One study found that levels of histamine, tryptase and leukotrienes were increased following exercise in sputum of people with exercise induced bronchoconstriction. This same study found that in these patients, prostaglandin E2 and thromboxane B2 was decreased in sputum. Treating with montelukast and loratadine suppressed release of leukotrienes and histamine during exercise.

One important area of research is the interface between being asthmatic and being obese. Adipose tissue is known to release inflammatory molecules called adipokines. In particular, the adipokine leptin has been studied for its role in bronchoconstriction following exercise. Leptin (I did a previous post on leptin, which is also called the obesity hormone) enhances airway reactivity, airway inflammation and allergic response. It can also enhance leukotriene production. This last fact is interesting because obese asthmatics are less likely to respond to inhaled corticosteroids when compared to lean asthmatics, but both respond similarly to anti-leukotriene medications like montelukast.

LTE4 was found to be significantly higher in the urine of both obese and lean asthmatics following exercise. It was not increased in either obese non-asthmatics or healthy controls. Additionally, the level of LTE4 was significantly higher in obese asthmatics compared to lean asthmatics. In this same study, urinary 9a, 11b-PGF2 was elevated in both lean and obese asthmatics, but not in obese or healthy controls. The 9a, 11b-PGF2 level was also higher in obese asthmatics than lean asthmatics. The elevated LTE4 and 9a, 11b-PGF2 were found in urine testing rather than in sputum, indicating that these chemicals did not stay local to the lungs and airway.

It is thought that the high levels of leptin found in asthmatics drive the manufacture and release of leukotrienes and prostaglandins from mast cells, epithelial cells or eosinophils during exercise. Though the data are stacking up to look like this is the case, there has not yet been a definitive causal link established.

 

References:

Teal S. Hallstrand, Mark W. Moody, Mark M. Wurfel, Lawrence B. Schwartz, William R. Henderson, Jr., and Moira L. Aitken. Inflammatory Basis of Exercise-induced Bronchoconstriction. American Journal of Respiratory and Critical Care Medicine, Vol. 172, No. 6 (2005), pp. 679-686.

Hey-Sung Baek, et al. Leptin and urinary leukotriene E4 and 9α,11β-prostaglandin F2 release after exercise challenge. Volume 111, Issue 2, August 2013, Pages 112–117

 

Histamine depletion in exercise

A long known and often repeated finding is that regular exercise can be protective against asthma. This finding was published in 1966 by a group that found the airways of asthmatics grew progressively less reactive following intervals of exercise. This finding was confirmed by several studies that followed. At the time, the reason why exercise protected against reactive airways was unclear, but an early hypothesis was that mediators were depleted after the initial round of exercise and that time was required to restore them.

In the 1980’s, there was a wave of research around the role of histamine in airway reactivity of asthmatics. There were a few competing theories at this point for why asthmatics became less reactive following exercise: depletion of mediators, mainly histamine from mast cells; that bronchial smooth muscle became less responsive to stimulation by histamine via the H1 receptor; and that release of catecholamines (such as epinephrine) by exercise suppresses bronchoconstriction. A number of studies made relevant findings.

Histamine is known to be released in the lungs due to exercise. It is also known to become depleted and quickly metabolized. When exposed to histamine, asthmatics recover quickly from the ensuing bronchoconstriction. Some asthmatic patients show an increase in plasma histamine during exercise.

Plasma epinephrine does not rise in asthma patients as a result of exercise, or at the very least is metabolized almost immediately, and thus is unlikely to be protective. Bronchial smooth muscle was not found to become less responsive to histamine. This was demonstrated in a study that compared repeated inhalation of histamine (such as might be induced by exercise) with actual repeated exercise. This study found that repeated exercise diminished airway reactivity, while repeated inhalation of histamine did not.

Another report indicated that inhalation of cromolyn before exercise can prevent or mitigate exercise induced asthma in most patients. Administration of H1 inverse agonists was found to offer similar protection.

A more recent study (2012) looked at the role of histamine in fatigue from exercise. Histamine is now known to be involved in regulation of oxygen/carbon dioxide exchange, which is important in exercise. In mice that were persistently exercised, the level of histidine decarboxylase was increased. HDC is the enzyme that makes and immediately releases histamine in response to an immediate need. This is different from degranulation, in which histamine is made ahead of time and stored inside the cell until needed.

This study found that treating the mice with an H1 antihistamine, H2 antihistamine, or HDC inhibitor decreased endurance in the mice. Mice deficient in HDC or H1 receptors also had less endurance. This means that histamine is partly responsible for inducing tolerance to exercise and that blocking action of histamine causes fatigue to set in more quickly.

Treatment with fexofenadine, an H1 antihistamine, decreased levels of nitric oxide and glycogen in the muscles of exercised mice. Taken together, these findings mean that histamine protects against fatigue from exercise; that this effect is achieved via H1 receptors and production of nitric oxide; and that at least some of this histamine is provided by immediate production and release of histamine via HDC. This means that your body does not simply release its histamine stores in response to exercise; it makes it on the fly so as not to exhaust its supply.

 

References:

Hahn, Allan G., et al. Histamine reactivity during refractory period after exercise induced asthma. Thorax 1984; 39: 919-923.

Niijima-Yaoita, Fukie, et al. Roles of histamine in exercise-induced fatigue: favouring endurance and protecting against exhaustion. Biol Pharm Bull 2012; 35; 91-97.

Schoeffel, Robin E., et al. Multiple exercise and histamine challenge in asthmatic patients. Thorax, 1980, 35, 164-170.

Graham P, Kahlson G, Rosengren E. Histamine formation in physical exercise, anoxia and under the influence of adrenaline and related substances. J. Physiol., 172, 174—188 (1964).

McNeill RS, Nairn JR, Millar JS, Ingram CG.Exercise-induced asthma. Q J Med 1966; 35: 55-67.

 

Anti-inflammatory properties of H1 antihistamines

H1 antihistamines are also known to have anti-inflammatory properties. Some studies show that H1 antihistamines prevent histamine release, which is actually independent of the ability to bind H1 receptors. This effect is thought to occur by interfering with calcium activity on the cell membrane, which may be important in signaling to a cell to release histamine. However, other studies say the amount by which histamine release is reduced is not significant clinically.

H1 antihistamines have also been observed to reduce eosinophil accumulation near allergic sites. This may be due to the ability of H1 antihistamines to interfere with activation of a molecule called NF-kB. This molecule is important in production of inflammatory cytokines. NF-kB can be activated by several inflammatory molecules, including histamine and TNF. Low concentrations of cetirizine and azelastine have been shown to result in lower levels of NF-kB while also inhibiting the production of IL-1b, IL-6, IL-8, TNF and GM-CSF.

Bradykinin is a mediator released by mast cells that causes inflammation, pain and edema. H1 antihistamines such as chlorpheniramine and cetirizine have been reported to inhibit bradykinin induced formation of hives, which may mean that bradykinin triggers hitamine release, which in turn participates in hive formation. However, in testing, the amount of histamine found in these reactions was minimal. This implies that H1 antihistamines may be able to inhibit bradykinin action in another way. H1 antihistamines have also inhibited weal and flare responses by methacholine and platelet activating factor (PAF).

References:

Church, Diana S., Church, Martin K. Pharmacology of antihistamines. World Allergy Organization Journal 2011, 4 (Suppl 3): S22-S27.

Leurs, R., et al. H1-antihistamines: inverse agonism, anti-inflammatory actions and cardiac effects. Clinical and Experimental Allergy 32 (2002): 489-498.

Pharmacology of H1 antihistamines

H1 receptors are a type of G-protein-coupled-receptors (GPCRs), and exist in two different conformational states. A conformation is a shape, and the way a receptor is shaped affects its activity. One of the H1 receptor conformations makes it active, so it is effectively the “on” position. The other makes it inactive, so it is effectively the “off” position.

When histamine binds to the H1 receptor, it keeps the receptor in the “on” position. This causes many things to occur. If too many H1 receptors are bound in the “on” position for too long, it can cause airway constriction, difficulty breathing, dilation of blood vessels, hiving, pain and itching, among other symptoms.

In pharmacology, two terms are used to describe the effect a substance has when it binds to a receptor. An agonist fully activates the receptor it binds to. Histamine is an agonist of the H1 receptor because when it binds the receptor, it activates it and thus turns it on. An antagonist binds the receptor but doesn’t turn it on (which is not the same as turning it off). By the antagonist binding the receptor, it prevents histamine from binding there are turning it on.

The medications we use to mediate H1 receptor actions, like diphenhydramine or cetirizine, are often called H1 antagonists, but this is a misnomer. All known medications that act on H1 receptors are more correctly classed as H1 reverse agonists, which is a trickier concept. Basically this means that when these medications bind the H1 receptor, they turn it off. In turn, this prevents a series of actions that are executed by the action of histamine.

First generation H1 antihistamines have a wide ranging group of effects. I have described receptors in the past as being like locks, and the substances that bind them (called ligands) are like keys. In this analogy, first generation H1 antihistamines like diphenhydramine would be like a master key. They are capable of binding to many receptors, including muscarinic, serotonin and a-adrenergic receptors. They also cross the blood-brain barrier. Histamine is an important neurotransmitter with a lot of activity of the brain. By crossing into the brain, these first generation H1 antihistamines can interfere with the sleep-wake cycle, learning, memory, fluid balance, regulation of body temperature, regulation of the cardiovascular system, and stress release of ACTH and b-endorphin from the pituitary.

During the day, first generation H1 antihistamines often cause sleepiness, sedation, drowsiness, fatigue and impaired concentration and memory, even at recommended doses. At night, they delay the onset and reduce the duration of REM sleep. This in turn causes a lower quality sleep, with decreases in attention, vigilance and working memory still observable in the morning.

Second generation H1 antihistamines have largely dealt with the issues present in first generation formulations. Unlike first generation medications, they bind with excellent specificity to the H1 receptor, rather than binding promiscuously. They demonstrate very limited penetration of the blood brain barrier so there is little associated sedation. Desloratadine in the most potent antihistamine, followed by levocetirizine and then fexofenadine.

H1 antihistamines are universally well absorbed with the exception of fexofenadine, which relies on a unique transport mechanism that can be more variable. Studies have shown that in adults, the maximum inhibition of allergic response occurs about four hours after taking levocetirizine, fexofenadine or desloratadine. Loratadine requires metabolism to release the active portion of the molecule, and thus can take hours longer to become efficacious. Fexofenadine has a shorter duration of action at about 8.5 hours, compared to 19 hours for cetirizine at a typical dose.

References:

Church, Diana S., Church, Martin K. Pharmacology of antihistamines. World Allergy Organization Journal 2011, 4 (Suppl 3): S22-S27.

Leurs, R., et al. H1-antihistamines: inverse agonism, anti-inflammatory actions and cardiac effects. Clinical and Experimental Allergy 32 (2002): 489-498.

A comprehensive list of antihistamines: H1 receptor (part 1)

Alimemazine, also called trimeprazine, is a phenothiazine derivative, placing it in the same class as the more well known promethazine. It is used for a variety of purposes, including antipruritic (prevents itching), sedative, antiemetic, anxiety disorders, organic mood disorders and sleep disorders. It is a first generation H1 antagonist. It is not available for use in the US, but is available in many other countries, including several European countries, Japan, Taiwan, South Africa, Australia, New Zealand and throughout the Middle East.

Azatadine is a first generation H1 antagonist with structural similarities to loratadine. It is available as Zadine in India (note: Zadine is a brand name used in several countries for multiple drugs). It is used to treat allergic symptoms.

Bamipine is a first generation topical H1 antagonist used for itching and allergic rashes. It is sometimes combined with hydrocortisone and sold as a cream or gel. It is available in Austria, Germany and Poland.

Benztropine, also called benzatropine, is a first generation H1 antagonist. It is most commonly used in the treatment of Parkinson’s disease, and Parkinson-like symptoms, particularly tremors. It can also be used to treat dystonia. Benztropine is a widely acting medication. It also acts as a dopamine reuptake inhibitor, which can be helpful in treating narcolepsy and attention disorders, and a functional inhibitor of acid sphingomyelinase, which is sometimes used to treat depression. One study found that benztropine decreased symptoms and encouraged nerve re-myelination in MS patients.

Bepotastine is a non-sedating, second generation H1 antagonist. It is available as an oral and ophthalamic mediction in several Asian countries under the brand name Talion, with ophthalmic preparation only available in the US as Bepreve. Bepotastine has been well studied. In adult models, it inhibited histamine, antigen and PAF induced skin reactions, systemic shock, airway constriction and maintained appropriate vascular permeability. It may also inhibit leukotriene B4, NO production and substance P.

Brompheniramine is a first generation propylamine H1 antagonist. It is used for general allergic symptoms and is found over the counter in many countries. Additionally, it functions as a serotonin and norepinephrine reuptake inhibitor, giving it antidepressant properties. The first SSRI was derived from brompheniramine. It also potentiates the effects of opioid pain medication so less pain medication can be used.

Buclizine is an H1 antagonist derived from piperazine. It is mostly used for nausea. It is available in several countries, including India, Taiwan, Singapore and multiple European nations. In the UK, buclizine is available in a combination migraine medication, Migraleve.

Captodiame is an H1 antagonist derived from diphenhydramine. It is also a serotonin receptor antagonist and dopamine receptor agonist. It has antidepressant effects via a unique mechanism that raises brain-derived neurotrophic factor in the hypothalamus only. It can also mitigate CRF activity in the hypothalamus.

Carbinoxamine is an H1 antagonist readily available in many countries, including in the US. It is often combined with other medications, such as decongestants. It is used for urticarial, angioedema, dermatographism, hay fever and allergic rhinitis and conjunctivitis.

Chlorcyclizine is a first generation H1 antagonist derived from phenylpiperazine. It is used for general allergic symptoms and as an antiemetic. It also has local anesthetic properties and antagonizes serotonin receptors.

Food allergy series: Mast cell food reactions and the low histamine diet

When I started my posts on food allergies, I listed out the causes of food hypersensitivity. Notably absent from this list was mast cell disease. Even among detailed publications on mast cell disease, food reactions are often unmentioned (though potentially subsequent anaphylaxis is usually included.) Unfortunately, food reactions in mast cell disease are still not well understood. Even among experts, the nature and importance of food reactions in overall disease is the subject of much disagreement. Some contend that food reactions are a manifestation of general mast cell reactivity, while some think the foods specifically are sources of reactions. Following this logic, some experts believe in the validity of observing a low histamine diet while others do not.

So please keep in mind that the science behind the low histamine diet is not well accepted or even well defined. I’m going to give you my general comments on the low histamine diet, how I eat and how it has worked for me. It is my personal opinion.

A low histamine diet is one which eliminates or minimizes histamine in the food consumed. I have talked at great length about histamine so I’m not going to reiterate that here. What I will say is that exogenous histamine has been shown to induce mast cell degranulation, which means that histamine from an outside source can cause degranulation. It makes sense to me as a scientist that eating histamine rich foods will cause mast cell degranulation. It especially makes sense because the most commonly problematic food substances for mast cell patients, like alcohol, vinegar and aged cheeses, are major degranulators. I have never been able to tolerate alcohol, so it made sense to me that it was because of degranulation. Again, I prefer to lean on good studies, but in the absence of that, I will accept my own experience living in this body.

Last winter, I was in a lot of pain and generally having a sucky time of life. One of the changes I discussed with my doctors was the low histamine diet. It was in the “this can’t hurt” category. I had put off elimination dieting for a long time due to time and financial constraints, but it seemed like the appropriate time to do it had arrived.

One of the first things that became aware to me was that there is no universally agreed upon low histamine diet. There are lots of websites that discuss it and lay out diet guidelines and none of them are in complete agreement. So I just picked the one that seemed the most reasonable to me and went from there. As a mast cell patient, any diet you pick will require customization.

The diet I picked was the Histamine and Tyramine Restricted Diet by Janice Joneja. It can be found on the Mastocytosis Society Canada page.   I like this diet a lot. I do not know Dr. Joneja personally, but when I read diet/nutrition articles by her, I find them to be based in science. They meet my common sense rule. I’m going to summarize the general guidelines of the diet below along with my comments.

Key guidelines for a low histamine diet:

  • Anything fermented should be avoided. Fermentation produces histamine as a side product. Some are only sensitive to yeast fermented products while some find that fermentation from any organism is triggering.
  • No preservatives and no dyes.
  • No leftovers and nothing overly ripe. This is one of the harder parts of this diet, but I find it very important. Fresh or frozen products seem okay. I have mixed success with thawing frozen meat, but lots of people do it successfully. The key is to not cook something, put it in the fridge and eat it three days later.
  • No canned products.
  • No pickled products.

Milk and milk products: Avoid fermented products, like cheeses of all kinds, kefir, yogurt, sour cream, cottage cheese and cream cheese. A fair amount of milk products are allowed. Milk (cow, goat, coconut) is allowed, as are cheese type products that are made without fermentation (mascarpone, ricotta, panir.) Some versions of this diet allow mozzarella cheese and I find that it is safe for me. Ice cream is allowed if it doesn’t contain other disallowed ingredients. Cream products are okay, too.

Grains, breads: Yeast is the component most likely to be triggering in these products. Many people choose to restrict gluten due to their individual biologic reactions to it. Gluten is not specifically restricted on this diet, but I can tell you that it basically ends up being excluded anyway because gluten containing products usually also contain yeast. Pure, unbleached flour or grain of any kind is allowed. Products that use baking powder for leavening are allowed, like biscuits, soda bread, scones and muffins. Crackers without yeast are allowed, as are cereals if they don’t contain excluded ingredients, including artificial dyes or preservatives. I have a very difficult time finding low histamine baked products that are premade, so I generally make my own. It is surprisingly easy to make good tasting baked products with safe ingredients at home.

Vegetables: The list of vegetables that aren’t allowed feels really disjointed and counterintuitive. There is not much to do beyond committing it to memory. Not allowed: potato, avocado, green beans, eggplant, pumpkin, sauerkraut, spinach, sweet potato, tomato, any overly ripe vegetable. I personally can eat potato and sweet potato without any problem and do pretty much every day. Removing tomato was a revelation for me. It’s hard to live around because we use it for so much, but I really feel so much better. I will sometimes have a little for immediately get a stuffy nose and headache. All other vegetables are allowed. Any green that is NOT spinach is allowed. I eat a huge amount of squash, which is a really versatile ingredient. I get lots of different types from supermarkets or farmers’ markets and I make soups, purees, baked squash, squash lasagna, squash steaks, and a million other things. I can always tolerate it. This diet has also pushed me to get familiar with less common ingredients, like taro root, breadfruit and lotus root.

Fruits: Again, the list of fruits that aren’t allowed doesn’t provide any obvious unifying factor to quickly identify something as safe or not. Not allowed: citrus fruits, including lemon and lime; berries, including cranberries, blueberries, blackberries, gooseberries, loganberries, raspberries, strawberries; stone fruits, including apricots, cherries, nectarines, peaches, plums, prunes; bananas, grapes, currants, dates, papayas, pineapples, raisins. Allowed fruits: melons (keep in mind that some people may have an oral allergy syndrome reaction to melons), apple, pear, fig, kiwi, mango, passion fruit, rhubarb, starfruit (not safe for those with impaired kidney function), longans, lychees. I eat a lot of fruit, especially apples and mangoes.

Meat, fish and eggs: All shellfish are prohibited. They naturally have a huge amount of histamine. No processed meats (cold cuts.) Eggs are allowed if they are allowed. Raw egg white is a HUGE histamine liberator. Fish is allowed ONLY IF IT IS FRESHLY CAUGHT, GUTTED AND COOKED. There are differing opinions on what this means but several sources estimate it must be cooked in less than 30 minutes from catching. So unless you are or are married to a fisherman/woman, I think this is unlikely to happen. Any meat should be fresh or thawed from frozen. Leftover meat should not be consumed.

Legumes: Soy is the big culprit here because it’s in everything and is not allowed. Also not allowed: green peas, sugar or sweet peas, red beans and tofu. Everything else is allowed, including lima beans, chickpeas (I eat a ton of chickpeas), pinto beans, white beans, navy beans, black eyed peas, black beans, lentils (I also eat a ton of lentils), split peas, peanuts, and real peanut butter.

Nuts and seeds: All okay except for walnuts and pecans.

Oils: All okay except for oils that contain preservatives like BHA or BHT.

Spices: No anise, cinnamon, clove, curry, cayenne, nutmeg. Everything else is okay.

Sweeteners: No unpasteurized honey, chocolate, cocoa beans, cocoa. Most others are fine, including pasteurized honey, sugar (of really any kind), maple syrup, pure jams and jellies. This diet says plain, artificial sweeteners are okay. They are definitely not for me. One of the very first things I was told by mast cell specialist was not to use artificial sweeteners. So you can judge for yourself.

Drinks: A lot of drinks are restricted, including all teas. Most fruit juices and drinks have some type of unapproved ingredient. Milk, pure juices, water, mineral water and coffee are the allowed drinks. I also sometimes make “muddled” drinks where I crush some safe fruit with a mortar and pestle, make a simple syrup, and then put the muddled fruit in some soda water with some simple syrup.

Miscellaneous: Not allowed: Yeasts, yeast extract, all vinegars, flavored gelatin. Allowed: plain gelatin, cream of tartar, baking soda and baking powder.

The diet recommends a strict four week adherence to determine if it works. I think this is pretty accurate. I did it with no cheating for five weeks. It helped a lot. I slept better, I wasn’t swollen all the time and I was less nauseous. But there were some downsides. The first is that it is a royal pain in the ass if you work because you really have to cook every day. The restrictions on meat meant that I had meat about once every 2-3 weeks. Not everything freezes well so making a lot ahead of time isn’t always a good idea.

Finding recipes can be hard because the fact that they are labelled low histamine does not mean that they ARE low histamine. Please be very careful with that. I also find that some sources for low histamine recipes seem to assume a high level of economic freedom in food purchasing, as well as access to expensive and difficult to find ingredients. I can shop at Whole Foods, which has a knowledgeable staff and a good stock of ingredients for diets like these. There were several components I still cannot find. I also spent literally $1000 at Whole Foods for the five weeks when I initially did this diet.

One unexpected result of this diet was that it resensitized me to foods that I had become desensitized to. So foods that used to bother me a little now cause a severe reaction (sometimes anaphylactic, requiring epinephrine.) I understand that the reason for this is because these foods always caused reactions but I was effectively “used” to them so I didn’t notice. Regardless of the reason, my life is a lot more difficult foodwise than it used to be. I can “cheat” with some foods with medications but the reactions are still bad. I don’t always know how I feel about my choice to do the low histamine diet in my particular situation, but the fact is that since I did, I now am forced to observe a version of it, probably for life.

So that’s my run down on the low histamine diet.