Histamine Intolerance and Infertility

As we explore Histamine Intolerance and Infertility we will dive into the areas of Histamine Intolerance, Mast Cell Activation Syndrome and Reproductive Health.

Histamine Intolerance (HIT) and Mast Cell Activation Syndrome (MCAS) are conditions that are gaining increasing attention in both research and clinical settings in regards to their prevalence, causes, signs and symptoms, associated pathologies and the most appropriate diagnostic and treatment strategies. Or put another way, how many people have these conditions, what do they ‘look’ and ‘feel’ like and what can be done to diagnose and treat  effectively or help individuals living with them?

A lot has been discovered about HIT and MCAS in recent years, however the complex nature of these conditions means there is still much to learn. What we do know is that many of the female reproductive conditions we see in our patients at Fertile Ground can coexist and be exacerbated by HIT and/or MCAS across all life stages, from teenage years through to post-menopause.  Therefore, being able to detect and manage HIT and MCAS can make a big difference to your general and reproductive health and fertility if you are experiencing these conditions. 

What is Histamine Intolerance (HIT)? (H4)

First, the nerdy stuff. Histamine is involved in many important functions in the body including immunity, inflammation, brain and gastrointestinal function as well as many aspects of the menstrual cycle, conception, pregnancy and labour.1-3 So, you definitely need histamine in your life.

However, there can be too much of a good thing, and when there is excessive histamine in your body, problems can arise– this is where MCAS and HIT come in. 

At a basic level, HIT is where mast cells in your body release too much histamine as a result of internal and/or external triggers that we eat, drink or breathe in.4-7 MCAS is also where you can also have too much histamine (released by inappropriately activated mast cells), but histamine is not flying solo – it is accompanied by a lot other inflammatory mediators that can induce other adverse effects (including tryptase, leukotrienes and prostaglandins).8-10 

The result? You can experience a wide range of clinical signs/symptoms affecting one or multiple body organs or systems or a worsening of disease states (we’ll go into the specific signs and symptoms shortly). 

Why? Because histamine receptors are located in cells all around the body in many different organs and systems. (In cells, histamine acts like a key and receptors like a lock that sets off a range of processes in the cell which ultimately lead to these symptoms occurring). And if you are sensitive (or intolerant) to histamine, this means that the normal effects of histamine in your body are exaggerated, causing a more pronounced response.7,11-14 

What causes Histamine Intolerance (HIT) and Mast Cell Activation Syndrome (MCAS)? (H4) 

This is still being researched however what is currently understood, and what we see in clinical practice, is that for most individuals they are brought on by a combination of causes rather than one individual cause/trigger. (Meaning thorough clinical assessment is necessary to identify your individual triggers). 

This can include (but isn’t limited to): 

  • Genetics
  • Gender (more common in anyone born female)
  • Gastrointestinal dysfunction or disorders
  • Nutrient deficiencies
  • Diet
  • Medications 
  • Stress
  • Hormonal imbalances 
  • Environmental (pollen, dust mites, heavy metals, pesticides, mould)
  • Toxin exposure
  • Hypersensitivity disorders


What does it look and feel like to have Histamine Intolerance (HIT) and Mast Cell Activation Syndrome (MCAS)? (H4)

So, if you have HIT and MCAS, what does it look and feel like? 

Because of the pathophysiological nature of HIT and MCAS, the multiple factors that can trigger them (as listed above) and our individual biology, the type and severity of the signs and symptoms commonly experienced such as those listed below, varies significantly. How it looks and feels can differ substantially from one person to the next. 

If you have HIT, you can experience multiple signs/symptoms that vary in their severity, duration and frequency that are triggered by high histamine levels.22 Conversely, individuals with MCAS exhibit signs/symptoms in at least two, but more commonly multiple organ systems in an episodic and recurrent manner with elevated blood biomarkers (primarily tryptase, less commonly histamine, leukotrienes, prostaglandins).9,18,19 

(Note that many of these signs and symptoms can occur with other pathologies, so experiencing these does not definitively confirm the presence of HIT or MCAS until other disease states have been ruled out via a thorough clinical assessment). 

Signs and symptoms:

  • Integumentary (eczema, dermatitis, urticaria (rashes), pruritus (itchy skin), flushing, oedema (swelling/fluid retention))
  • Gastrointestinal (abdominal distension, constipation, postprandial fullness (after eating), cramping, nausea, vomiting, diarrhoea, abdominal pain and constipation) 
  • Nervous system (anxiety, dizziness, headaches, migraines, impaired concentration or ‘brain fog’, sleep disruption) 
  • Respiratory (sneezing, rhinorrhea (runny nose), nasal congestion, swelling, phlegm, cough, asthma, throat swelling, wheezing) 
  • Muscular (pain) 
  • Cardiovascular (tachycardia (irregular heart beat), hypotension (low blood pressure), syncope (fainting)).


How can Histamine Intolerance (HIT) and Mast Cell Activation Syndrome (MCAS) affect your reproductive health and fertility? 

As if experiencing the signs/symptoms listed above isn’t enough, let’s take a closer look at Histamine Intolerance, MCAS, Infertility and Reproductive Health. HIT and MCAS can also affect your reproductive health and fertility, because histamine also interacts with hormones involved in the menstrual cycle, implantation, conception, pregnancy and labour, particularly oestrogen, which (also) stimulates the production of histamine.3,24-26

So, women with HIT or MCAS have something of a double-whammy – they already get an exaggerated response to histamine in the body and then more histamine can be produced as a result of elevated oestrogen levels.3,24-26 This can then cause or exacerbate existing reproductive health and fertility difficulties, with associated pathologies currently understood to include: 

  • Oestrogen excess
  • Menstrual headaches/migraines
  • Premenstrual symptoms 
  • Dysmenorrhoea (period pain)
  • Menorrhagia (heavy bleeding)
  • Dysfunctional uterine bleeding (abnormal bleeding)
  • Ovarian cysts
  • Endometriosis
  • Pelvic adhesions
  • Interstitial cystitis 
  • Dyspareunia
  • Implantation difficulties
  • Recurrent miscarriages
  • Mastitis (breast swelling and pain)
  • Lactation suppression (reduced breast milk supply)
  • Postpartum haemorrhage (abnormal heavy bleed after birth)
  • Postpartum depression or anxiety

      10, 27-32

What can you do if you think you have Histamine Intolerance (HIT) and Mast Cell Activation Syndrome (MCAS)?

The good news is there is much that can be done to alleviate the clinical signs and symptoms associated with HIT and MCAS and improve the adverse influence it is having on your reproductive health and fertility.

In keeping with the holistic approach that underpins naturopathic medicine, the strategies used usually include a combination of functional pathology, dietary modifications, nutrient, herbal and lifestyle changes, however the specifics will vary between individuals according to their individual needs. 

This is because while the clinical presentation of HIT and MCAS can be similar between people (or also be completely different!), the internal and external factors that are causing them and how these conditions are affecting how your individual body functions is significantly diverse both from one person to the next, and in the same individual at different life stages. 

It can certainly be a complex puzzle to work out for someone experiencing the signs and symptoms of HIT and MCAS, and it is something that I really enjoy working with. The often immediate relief and results we get over time speak for themselves and it can be truly life changing if this is something that is affecting you. Please do reach out if you think I may be able to help you. 


Georgia Marrion Senior Fertility Naturopath Written by Senior Fertility Naturopath & Nutritionist, Georgia Marrion

Georgia is a naturopath of 19 years’ experience with a Degree in Complementary Medicine and a Masters in Nutrition. Along with extensive clinical experience in reproductive health and fertility, Georgia is also an experienced writer and well regarded speaker.


Are you experiencing any of the above signs and symptoms? Or perhaps you’re keen to investigate whether HIT or MCAS could be impacting your fertility? 

Book your free 10-minute introduction telehealth consult with Senior Fertility Naturopath & Nutritionist, Georgia Marrion to get started. Navigate to Naturopathy – Fertile Ground > 10-minute Free Naturopathic Introduction TELEHEALTH


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