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Food Sensitivities or Histamine Intolerance: What’s Actually Causing Your GI Trouble?

Years ago, I was talking to my mentor about my frustration with not feeling my best. As a functional nutritionist, I was starting to feel like a fraud. Here I was trying to help people feel better using an integrative approach, which I whole-heartedly believe in and see changing lives every day. I’m an expert in wellness and precision nutrition for the individual and I couldn’t seem to help myself feel better. I knew there had to be something I was missing and I’d already discovered there was nothing obviously diagnosable. As usual, all of my labs from my provider were normal. Everything I did didn’t seem to work anymore.

I had all these nonspecific symptoms: brain fog, fatigue, poor sleep, itchiness, and GI complaints, some of them I had never experienced before. Nonspecific means that they aren’t attributable to any one specific cause. They are seen in many conditions, therefore, it’s difficult to determine what the cause is and often is attempted to be determined through elimination of potential causes starting with the most obvious.

 I also had these random unexplainable things like flushing, unexplained weight gain, decrease in appetite, hair loss, and many other random things. It all seemed to hit me like a wave one summer after we moved. I remember saying to my husband as I was carrying boxes: “I think I have an allergy to cardboard or something. Every time I move a box my hands get red and itchy and it takes forever to go away.” I later noticed this same thing when I would mop or sweep, and when doing things like practicing yoga. Anything where pressure was on my hands.   

It was all just…weird. More importantly, it was significantly impacting my day to day and it was putting me in a bad mood which was negatively impacting my household. Fast forward to this conversation with my mentor who told me…I think you have an issue with histamine.

What the heck?!

I did not understand what she meant at first. I’d never had much in the way of seasonal allergies or anything. After all, when you hear the word “histamine” don’t you just think of seasonal allergy medications or Benadryl? I would quickly learn what it all meant, and eventually our practice would become a hub for many who are suffering from histamine intolerance and Mast Cell Activation Syndrome also known as MCAS (em-CASS).


What is Histamine Intolerance (HI)?

Histamine Intolerance is when “a disproportionate amount of histamine in the body is thought to result from the consumption of food with high histamine content, and reduced ability of mainly the enzyme diamine oxidase (DAO) to digest histamine.”1 In studies, many of those with HI do not have a deficiency in the DAO enzyme. This is likely because there is more than just one enzyme that breaks down histamine. There is still research to be done to understand HI more, but we do have data that it can be genetically driven.

 Symptoms often show up in the GI system and they often include bloating, but can lead to diarrhea or constipation depending on the person.2 There are many symptoms that show up outside the GI tract as well…more on that later.  


What is Mast Cell Activation Syndrome (MCAS)?

 To keep it simple: MCAS is much more complex than HI and usually involves the immune system and inflammatory pathway activation far beyond the release of histamine. It can range from mild to severe, even including anaphylaxis, depending on the person and cause. We all have mast cells all over our body and they do release histamine as well as other inflammatory mediators, etc. Some with MCAS have an increased number of mast cells in their body or a genetic predisposition to MCAS.

 There is specific testing for MCAS that can include tryptase levels (an increase specific to MCAS sufferers), 24-hour urine histamine levels, urinary histamine metabolites and prostaglandin metabolites. Measuring things like DAO in both MCAS or HI is still under review as are a few other tests. Like HI, research is ongoing.3


What are the Symptoms of HI or MCAS?

 As mentioned before, this is so hard to nail down if your healthcare provider is not aware of this condition. I’ve actually had a primary care doctor tell one of my clients that it wasn’t a real condition. If I could write a book of misleading or untrue things I’ve heard in my career, it might be a bestseller. If they had listened to this doc rather than what I was telling her they would still be majorly suffering today. After 30 years of unexplained symptoms that no provider could figure out, they finally had a path and made a major recovery.

 There is such a growing body of research on HI and MCAS that it’s impossible to say it’s not real. Most commonly though, providers who don’t specialize in this area may not be familiar with or even aware of it at all, making it challenging for you to get help. We do not blame doctors for not knowing about it, there are SO many things to know out there and it’s challenging to keep up, especially under the conditions of rapidly changing scientific research..

 Symptoms are often non-specific, making it so much more difficult to get help or understand what’s going on in your body. Histamine Intolerance and MCAS are often mistaken for food sensitivities, but that’s not entirely what’s occurring; sometimes food intolerances are a PIECE of it, but typically not the whole issue.


Most common symptoms we see are:

  • Fatigue
  • Weight Gain or Loss
  • Headaches
  • Brain “fog” or cognitive changes
  • Cold intolerance
  • Flushing
  • Dermatographism (remember the red itchy hands from the pressure of the cardboard box and mop?)
  • Hormone/Period Changes
  • Appetite Change
  • Increased Thirst
  • Hair Loss
  • Sinus Congestion or Post Nasal Drip
  • Itching
  • Rashes
  • Trouble Catching Your Breath (think…going up the stairs is harder than you feel it should be)
  • Swollen Lymph Nodes
  • Weakness
  • Blood Pressure Changes
  • Heart Palpitations
  • Bloating and/or Gas
  • Nausea
  • Abdominal Pain or Discomfort
  • Pelvic Pain
  • Painful Periods
  • Heavy Periods
  • Constipation or Diarrhea
  • Decreased Libido
  • Mood Changes: Anxiety, Depression, etc.
  • Thyroid changes (this can be a chicken/egg situation)
  • And more…


You will likely not experience ALL of these symptoms. How every person presents is unique. If you are experiencing what seems like food sensitivities along with a bunch of these other things, you could be a sufferer.


What are the Causes of HI or MCAS?

We’ve already touched on one potential cause: genetics.There are genetic markers that CAN indicate that you have an issue handling histamine. We run genetic tests on our clients to see if this is a potential piece of the puzzle.


Other Potential Causes:

  1. History of Trauma (usually early childhood) or Increased Stress

Research shows that early traumatic experience can have a huge impact on inflammation pathways as we age. In a similar way, increased stress can be a huge trigger especially if you’re constantly taking shallow breaths or have a lot of bodily tension.

  1. Infections

This could include parasitic infections, opportunistic bacterial infections in the gut as well as other types of bodily infections.

  1. Leaky Gut

Intestinal permeability, where your immune system starts reacting to things due to changes in the tight junctions that protect us by keeping the things inside our GI tract from contacting things outside of it.

  1. Mold or other Toxin Exposure

The kicker for this one is that sometimes this can show up YEARS after the acute exposure. You may have been exposed to toxic mold in an old apartment 10 years ago and not at all since then that you know of. Those that don’t have good quality detox pathways can be sufferers.

  1. Hormone Imbalances

I see this start to pop up in women who have an imbalanced estradiol to progesterone ratio (not necessarily out of lab range) and more commonly in perimenopausal women. When progesterone starts dropping, the histamine can come a-knocking. It is also uncanny how many times I see this alongside those with endometriosis as well.

 It’s also not uncommon to see histamine issues show up as more than one potential cause. I’ve seen genetic predispositions in those with a parasitic infection, previous mold toxicity while starting perimenopause. DUDE…I know…


The Problem with Histamine, MCAS and Dr. Google…

 There is a lot of misinformation out there in regards to histamine intolerance, especially in regards to dietary changes. One source will say one thing and another will say the opposite. We always suggest our clients stop using Dr. Google to allow us (or someone who specializes) to lead them on this one because every situation is highly individual and working with a specialist can really help tone down the noise and confusion. Part of the reason a lot of sufferers come to us is because of how confused they have become after months, or even years, of self-research.


How are HI or MCAS Treated?

Antihistamines and Mast Cell Stabilizers (for MCAS) are often prescribed to help manage symptoms, but most of the time that’s not enough by itself. Most sufferers may notice temporary relief for a very short period (sometimes only an hour) before symptoms return when the approach is only medication. Those who know and understand these conditions the best understand that the dietary component, and in some cases, supplements, are needed to really make a difference. Working with a Certified Nutrition Specialist who specializes in MCAS and HI is really an important piece to improving. In fact, we have multiple doctors who refer to us for this because they know how important it is for these patients.

If a healthcare provider tells you that diet won’t help you…they’re typically wrong. We have yet to see a patient not improve significantly while working with us. I see massive changes in my clients and many of them sought my help even when their provider told them dietary changes or “natural” approaches wouldn’t help them.

When you deal with the underlying causes including diet, sometimes supplements, and lifestyle support, you can often see your life completely turn around or at least become much more manageable than before. The start is finding the root cause of the issue and addressing it in a personalized way. We believe in personalized nutrition and no two HI or MCAS sufferers present exactly the same way…even from a dietary perspective. I have clients that can tolerate a food that another one absolutely cannot.

It can be some trial and error which is why it’s SO important to have someone who knows working with you to help lead you down the right path. This can also be a highly emotional journey as well because the adjustment can shift the way you’ve been doing things up until now and that shift isn’t always easy. It’s important to have support through the process.


If you think you might be suffering from one of these two things, set up a discovery call with us so that we can learn more about you and your situation and see what we can do to help.




  1. Schnedl WJ, Lackner S, Enko D, Schenk M, Holasek SJ, Mangge H. Evaluation of symptoms and symptom combinations in histamine intolerance. Intest Res. 2019 Jul;17(3):427-433. doi: 10.5217/ir.2018.00152. Epub 2019 Mar 7. PMID: 30836736; PMCID: PMC6667364.
  2. Cimolai N. Comparing histamine intolerance and non-clonal mast cell activation syndrome. Intest Res. 2020 Jan;18(1):134-135. doi: 10.5217/ir.2019.00087. Epub 2020 Jan 30. PMID: 32013319; PMCID: PMC7000637.
  3. Valent P, Akin C, Nedoszytko B, Bonadonna P, Hartmann K, Niedoszytko M, Brockow K, Siebenhaar F, Triggiani M, Arock M, Romantowski J, Górska A, Schwartz LB, Metcalfe DD. Diagnosis, Classification and Management of Mast Cell Activation Syndromes (MCAS) in the Era of Personalized Medicine. Int J Mol Sci. 2020 Nov 27;21(23):9030. doi: 10.3390/ijms21239030. PMID: 33261124; PMCID: PMC7731385.
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Autumn is the Founder and CEO of HopeWella Nutrition in Los Angeles, California. Featured in publications, podcasts and documentaries, such as Eat Play Diet, she is well-known in and around Southern California as a nutritional specialist in the areas if Digestive Health, Hormone Balance, Histamine Intolerance and Mast Cell Activation Syndrome, Nutritional Genetics and Metabolic Health.

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