You probably know someone (or a few people) with a food intolerance or allergy—that’s how common they are. But for those who haven’t been able to pinpoint a specific food that’s causing their symptoms or who have intermittent reactions to certain foods, there may be something else going on: histamine intolerance. Most people have never heard of it, but it’s more common than you might think.
What is histamine, exactly?
The name “histamine intolerance” might make it seem as if it’s a bad thing, but that’s not the case. “Histamine is awesome,” says Sanna Kalika, MD, an internal medicine doctor at Parsley New York City. Histamine is a chemical made by the immune system that’s released from mast cells, a type of white blood cell. This happens in response to injury or allergen, and is the beginning of the inflammatory process, she explains.
If you come into contact with something you’re allergic to or intolerant of, histamine will act on many different parts of the body, for example: dilating blood vessels, causing your lungs to constrict, releasing adrenaline, spiking your heart rate, increasing capillary permeability, which causes swelling, and causing your skin to itch. In other words, it causes an allergic reaction.
“Histamine also triggers the release of stomach acid, so it helps us with digestion,” Dr. Kalika adds. But when histamine goes rogue, people experience symptoms of a histamine reaction on a regular basis. This is known as histamine intolerance.
What causes histamine intolerance?
One thing to get out of the way: you can’t actually be allergic to or intolerant of histamine. “Histamine intolerance is simply having symptoms of too much histamine in the body,” Dr. Kalika clarifies. (So we call it a “histamine intolerance” even though it’s technically not.)
So why might that happen? We naturally produce a digestive enzyme called diamine oxidase (DAO) along with histamine that helps up break down the histamine we take in from food. (Almost all foods contain histamine, but some have much more than others.) DAO is produced by the kidneys, thymus, and intestinal lining.
But if we don’t have enough DAO, then we can’t break down histamine. “It can build up to high levels and cause symptoms, and these are the symptoms of histamine intolerance or overload,” Dr. Kalika notes.
According to Dr. Kalika, some common reasons for DAO deficiency include:
- Certain medications that block DAO production and/or function, such as NSAIDs and immune modulators
- G.I issues like leaky gut, gut dysbiosis, IBD, SIBO, and other GI infections
- Eating too many histamine-rich foods (such as avocado, eggplant, and fermented foods—see full list below)
- Alcohol use
Histamine intolerance can also be caused by mast cell dysfunction Dr. Kalika says, which can result in histamine overload. For example an underlying cause can be, mastocytosis, an increased number of mast cells or Mast Cell Activation Syndrome, which is an increase in activation of existing mast cells.
It’s hard to say how many people are dealing with histamine intolerance, but a review in the American Journal of Clinical Nutrition estimated that 1% of the population has it, with 80% of them being middle-aged.
The symptoms of histamine intolerance vary widely.
Because histamine can trigger an inflammatory response in so many parts of the body, the symptoms can be incredibly vague.
The list of potential histamine intolerance symptoms is long, but some of the most common are related to the cardiovascular system, Dr. Kalika says. These include:
- Flushing, difficulty regulating body temperature, sudden excessive sweating
- Hives, rashes, swelling, itchy skin, eczema
- Racing heart, palpitations, arrhythmia
- Low blood pressure
But symptoms can also occur in the:
- Respiratory system, such as difficulty breathing, coughing (acute or chronic), asthma, nasal congestion, sinus issues, sore throat, post-nasal drip, and throat clearing.
- Digestive system, such as nausea, vomiting, diarrhea, stomach pain, bloating, and acid reflux.
- Nervous system, such as headaches, migraines, vertigo, dizziness, insomnia, fatigue, and anxiety.
- Muscular system, such as muscle twitches, myalgia, arthralgia, and fibromyalgia.
- Reproductive system, such as period cramps, irregular periods, endometriosis, and estrogen dominance.
Because the symptoms are so varied, it’s usually diagnosed and treated by a process of elimination.
There are no standardized tests to diagnose histamine intolerance. A histamine pinprick test may help suggest histamine intolerance, but it’s not a conclusive test.
That’s why diet is usually the first step in both diagnosis and treatment. In her experience over the years, Dr. Kalika says there’s one thing patients say that gives her a heads up they could be dealing with histamine intolerance:
“When people say they feel better when they eat worse, I suspect they have histamine intolerance. Because when they eat healthy, they may inadvertently consume a lot of histamine-rich foods.”
But before going directly to a low-histamine diet, Parsley practitioners recommend a foundational diet, Dr. Kalika says. This usually involves eating protein, greens, and healthy fats on every plate, while avoiding refined carbs, refined sugars, and trigger foods like gluten, dairy, and soy. “This is because if someone has symptoms of histamine intolerance due to an allergy to gluten or soy, a low-histamine diet will not get to the root cause.”
If that doesn’t work, next up is a low FODMAP diet. FODMAP stands for fermentable oligo-saccharides, di-saccharides, mono-saccharides, and polyols, which are types of fermentable carbohydrates some people have a hard time digesting. This can be because of a bacterial imbalance in their intestine, like SIBO, a sluggish digestive system that increases the transit time of food through the gut, or both. If a low FODMAP diet helps, that’s a sign that SIBO may be a factor, says Dr. Kalika. “If SIBO is diagnosed, the goal of the treatment is aimed at eradicating SIBO itself.” Once SIBO has been resolved, the histamine intolerance symptoms should, as well.
Only after trying both of these diets without symptoms resolving does Dr. Kalika recommend a low-histamine diet.
What do you eat on a histamine intolerance diet?
Surprisingly, you don’t just avoid foods high in histamine. You also have to avoid foods that trigger histamine production and ones that block DAO production.
Foods that are high in histamines include:
- Fermented foods such as sauerkraut, soy sauce, and kimchi
- Vinegar and vinegar-containing foods such as pickles, mayo, olives
- Dairy products such as yogurt, kefir, sour cream and aged cheese
- Dried fruit
- Vegetables such as avocados, eggplant, and spinach
- Processed or smoked meats and fish, hot dogs
Foods that trigger histamine release include:
- Fruits such as banana, papaya, and citrus fruits
- Wheat germ
- Nuts, especially walnuts, cashews, and peanuts
- Food dyes and other additives
Foods that block DAO production include:
- Black and green tea
- Energy drinks
A histamine intolerance diet involves removing all the above foods. Then, each potential trigger food is reintroduced one at a time to watch for reactions. During this time, it’s important to focus on low-histamine foods such as:
- Fresh meat and fresh-caught fish
- Non-citrus fruits
- Gluten-free grains such as quinoa and wild rice
- Dairy substitutes such as coconut and almond milk
- Fresh vegetables except for tomato, avocado, spinach, and eggplant
- Cooking oils such as olive oil
“Diet-wise, some research also suggests that an adequate intake of healthy fats and other nutrients including phosphorus, zinc, magnesium, copper, iron and vitamin B12 may play a role in enhancing DAO activity,” Dr. Kalika says. So an overall balanced diet is key.
Sometimes, these dietary recommendations are also combined with other forms of treatment, including:
- Probiotics, since gut imbalance is a common cause of histamine intolerance
- Immunoglobulins, which boost the gut’s immune system, reducing histamine overproduction and improving DAO production
- Gut soothing supplements like L-glutamine
- Traditional antihistamines
It’s also worth noting that some doctors may not know to look for histamine intolerance. According to Dr. Kalika, that’s because while there’s a lot of evidence in practice that histamine intolerance is an issue, there isn’t much published clinical research about it.
The good news? If you have a histamine intolerance, addressing the root cause should help resolve it over time, meaning you can enjoy histamine-rich foods again without symptoms. Finding that root cause can be a challenge, though, Kalika notes. “But at Parsley, we make an effort to identify the causes or triggers and work on eliminating them.”