If you’re like most people, you have used an antihistamine before, and you might even be taking one pretty often to treat those hay fever symptoms or seasonal allergies. But, you might not have heard of histamine intolerance, or even know what histamine is. Furthermore, it’s possible that your daily antihistamine might not be the best long term solution to curbing those annoying allergies. In fact, it’s possible that they might not be allergies at all. This article will tell you all you need to know about a healthy histamine response, and when to suspect an intolerance to histamine.

Let’s start with the basics…

What is Histamine?

Histamine is a chemical released by your mast cells (a type of white blood cell) in response to a foreign invader or allergen. Histamine is also found in certain foods. For those who suffer from allergies, histamine is released upon exposure to the allergen. This could be pet dander, pollen, mold, dust, or one of the top 8 food allergens: wheat, milk, tree nuts, seafood, shellfish, eggs, soy, and peanuts.

Even though histamine release causes those familiar (and annoying) inflammatory symptoms like puffy, itchy or watery eyes, sneezing or wheezing and even hives, it’s important to know that histamine release is part of a healthy immune response. Those symptoms mean that your immune system is doing its job and attacking those foreign substances.

However, problems start when there is a buildup of histamine in the body. Think of a bathtub filling up with water. If the drain is open, the bathtub won’t overflow even if the faucet is on. However, if the drain is stopped, the bathtub will overflow as long as the faucet is running.

Now, apply this to histamine buildup. Your body is the bathtub, and the faucet is histamine release from mast cells or histamine ingested through foods. As long as the body can effectively metabolize histamine, you’re in the clear! But, when the body can’t, you get histamine overflow from foods high in histamine, as well as histamine released from our cells. This results in those pesky allergy symptoms.

This brings us to a critical question: What causes an overflow of histamine in the body?

What is Histamine Intolerance?

An enzyme called diamine oxidase (DAO) is responsible for clearing histamine from the body. Those with healthy DAO levels don’t experience symptoms associated with a histamine response unless they have a reaction to a food or environmental stimuli. However, some people have a deficiency of DAO most likely caused by a genetic mutation. Consequently, they experience histamine buildup also referred to as histamine intolerance. They feel as if they have allergies all year round, not just seasonally or in reaction to specific food or environmental triggers.

Histamine intolerance is very rare. In fact, a study published in The American Journal of Clinical Nutrition reported that it probably only affects about 1% of the population. It is difficult to diagnose and can be debilitating.  Note that a condition called mast cell activation disorder (MCAD) also presents similarly to histamine intolerance, which increases the difficulty of diagnosis. It’s important to talk to your doctor about an official diagnosis. In addition, there are steps you can take to identify whether you have a histamine intolerance, and ways to improve your symptoms!

How do I know if I am histamine intolerant? 

Someone with histamine intolerance will experience allergy symptoms without the presence of a true allergen. This is due to the buildup of histamine in the body over time, cumulating in a level of histamine in the body that produces symptoms.

Signs and symptoms include:

  • Hives (Urticaria) or Eczema
  • Chest tightness
  • Wheezing
  • Watery or itchy eyes
  • Swelling around the eyes or lips (Angioedema)
  • Feeling dizzy
  • Extreme fatigue
  • Headaches or migraines
  • Quick heart rate (Arrhythmia)
  • Flushing of the face or neck
  • Nausea
  • Constipation or Diarrhea
  • Low blood pressure

Are my symptoms the only way to tell if I’m histamine intolerant?

Ok, so you may check some of those symptoms off that list. But, these signs and symptoms can indicate many different problems and affect most people at some point in their lives. So, while having some of these physical markers might have you thinking you’re histamine intolerant, it’s important to gather more information through testing or dietary measures.

There are a few ways to determine if you have histamine intolerance. Since all of them limitations, it’s helpful to use these assessments in conjunction with the symptoms checklist.

  1. DAO Levels –

    • Measuring DAO levels can be a helpful tool, but it’s not a conclusive test for histamine intolerance. There are other enzymes that metabolize histamine, so if DAO levels are low, there might be other compounds that are working to clear histamine from the body.
    • Additionally, if you are a menstruating woman, testing DAO levels gets complicated. This is because DAO levels fluctuate with a woman’s menstrual cycle. Levels appear higher during the luteal phase and lower during the follicular phase, meaning symptoms will probably be at their worst during menstruation. This makes it difficult to get a truly accurate DAO reading.
    • DAO levels are also high during pregnancy because high concentrations of DAO are found in the placenta, so many woman will notice their symptoms are significantly decreased during their pregnancy.
    • Click here to learn more about this blood test. Although blood tests may easily be ordered online, it’s best to consult with a healthcare practitioner to ascertain whether the test is necessary. 
  2. Skin Prick –

    • This test is often used to determine food or environmental allergies. It works by introducing the suspected allergen to the skin and measuring wheel (a red, swollen mark) size. Exposing the skin to a histamine solution has been found to be an accurate measure of histamine intolerance when used in conjunction with patient history.
    • To find out more about how the skin prick test works talk to your doctor or click here.
  3. Elimination Diet –

    • An elimination diet is the gold standard when identifying histamine intolerance. Eliminate high histamine foods as well as those known to increase histamine release from mast cells for four to six weeks.
    • Then, a challenge is done of each food while tracking symptoms. If all or many high histamine foods produce allergic symptoms, it’s a fair bet that you are intolerant to histamines.
    • It’s best to work with a Nutritionist or Registered Dietitian who can support you through this process, and help you identify what foods are triggering your symptoms.

While Dr. Google and a plethora of information available online makes it tempting, please avoid self-diagnosing. Many conditions, like MCAD, present similarly to histamine intolerance and mimic the symptoms listed above. These include an IgE-mediated food allergy, food sensitivities, environmental exposures to an allergen or irritant, an intolerance to lactose or fructose (conditions characterized by a lack of the enzyme needed to break the sugar down) which can cause digestive irritation, or even mastocytosis.  

If you need help navigating your issues with histamine, let’s set up a personalized nutrition program

Stay tuned for part 2, where we discuss diet and supplements for histamine intolerance!


Guest article contributed by:

Elizabeth Herbert, MS candidate at the Maryland University of Integrative Health



Maintz, L., & Novak, N. (2007). Histamine and histamine intolerance. The American journal of clinical nutrition, 85(5), 1185-1196.

Kofler, L., Ulmer, H., & Kofler, H. (2011). Histamine 50-Skin-Prick Test: A Tool to Diagnose Histamine Intolerance. ISRN Allergy, 2011, 353045. http://doi.org/10.5402/2011/353045


Could Your Histamine Intolerance Really Be Mast Cell Activation Disorder?