When you hear the word histamine, drugs like Benadryl probably come to mind. It’s common to use antihistamines in the face of strong allergic reactions.

If histamine hasn’t given you much trouble other than a few runny noses in the spring, you probably haven’t given it as much thought.

On the other hand, if you suffer from severe allergies, histamine intolerance, mast cell activation syndrome (MCAS) or any other condition that causes your histamine levels to be higher or your body to less tolerant – then you know firsthand how powerfully histamine can rule over your life.

With chronic illness on the rise, I’m seeing higher incidences of histamine intolerance and mast cell activation syndrome in my practice. Though these conditions can have overwhelming symptoms, there’s a lot that can be done to keep them in check.

First, let’s take a step back and understand three critical concepts:

  1. How histamine affects the body.
  2. What you can do to reduce the impact of histamine over your life.
  3. How to boost DAO enzyme levels, which is responsible for breaking histamine down.

What is Histamine?

Histamine is an important part of your immune system because it causes necessary inflammation during times of injury and healing. Histamine is released from your mast cells, which are present in every tissue in your body. Mast cells release multiple chemical inflammatory mediators as part of your immune system response. Histamine is only one of these hundreds of chemicals your mast cells can release – though it gets a lot of attention.

Histamine is incredibly powerful. For example, in the case of someone who’s severely allergic to peanuts, the smallest taste can trigger a strong histamine response. When histamine is unleashed, it sends inflammatory signals throughout your body – to your gut, nose, throat, mouth, skin, and lungs. Histamine
is the chemical that’s largely responsible for the trademark allergic reaction.

When histamine runs rampant and unchecked, it can cause health complications like histamine intolerance and mast cell activation syndrome. A buildup in the body can happen because of excess histamine but also insufficient DAO levels.

The DAO Enzyme

Diamine oxidase (DAO) is an enzyme that’s responsible for breaking down histamine. Another enzyme responsible for breaking histamine down is called histamine N-methyltransferase (HNMH), but we are going to mostly focus on DAO because it’s much more effective.

DAO is mostly found in the kidneys and thymus. In pregnant women, DAO levels rise significantly and are found in the placenta. In the body, DAO breaks down histamine, which is then excreted through your kidneys and urine.

DAO is also found in the small intestine, in two sections called the jejunum and ileum. When foods high in histamine pass by this part of the small intestine, DAO breaks it down and prevents it from entering the body. When you have sufficient DAO, nearly all of the histamine that passes through your digestive
tract is broken down and therefore doesn’t cause any issues.

If you don’t have enough DAO, it can cause histamine levels to rise. If this goes on long enough, it can cause histamine sensitivity, chronic inflammation or mast cell activation syndrome.

If you suspect you have too much histamine or not enough DAO enzyme there are a couple of things you can do:

  • Reduce the histamine in your diet
  • Boost DAO enzyme
  • Avoiding DAO blocking foods

In general, avoiding histamine means avoiding old or aged food. This includes vinegar, alcohol, cured meats, smoked meats, fermented foods, canned foods, and leftovers. However, this is just a general rule of thumb and there are other foods that contain histamine

Boosting Your DAO Enzyme Levels

You can take DAO supplements, which will increase your levels in your digestive tract and enhance histamine breakdown of anything that’s eaten. However, DAO supplements do not get into your bloodstream and cannot increase your DAO levels internally. This means that supplementing with the DAO enzyme only helps you break histamine down that you’re consuming.

DAO enzyme supplements will not break down histamine that’s created by your mast cells – though this is still an effective treatment. This also means that DAO supplements cannot cure histamine intolerance or mast cell activation syndrome. Now you’re probably wondering how we can boost DAO naturally, within the body.

Scientists have found a number of nutrients that are effective at boosting DAO enzyme levels. These nutrients include:

  • Omega-3 fatty acids
  • Saturated fat
  • Phosphorus
  • Calcium
  • Zinc
  • Magnesium
  • Iron
  • Vitamin B12
  • DAO Boosting Foods

Foods that help boost DAO levels in your body and are also less likely to trigger histamine response include:

Omega-3 is an important one, they have been shown to release DAO and in women.

Eat more:

  • Olive oil
  • Wild caught salmon
  • Mackerel
  • Walnuts

*Be wary of fish oil supplements, which are very susceptible to oxidation.

Healthy saturated fats:

  • Grass-fed butter
  • Avocado
  • Fatty fresh fish
  • Pasture-raised chicken eggs (unless it’s a sensitivity)
  • Phosphorus:
  • Almonds
  • Broccoli
  • White beans
  • Pasture-raised chicken eggs (unless it’s a sensitivity)


  • Dark leafy greens
  • Broccoli
  • Beans
  • Lentils


  • Grass-fed meat
  • Almonds
  • Lentils
  • Spinach


  • Dark leafy greens
  • Pumpkin
  • Almonds
  • Cashews

Vitamin B12:

  • Grass-fed beef liver
  • Grass-fed beef
  • Wild caught salmon
  • Fresh tuna


  • Lentils
  • Pumpkin seeds
  • Grass-fed beef
  • Broccoli

Avoiding DAO Blocking Foods

If you’re having trouble with histamine, the number one thing you should avoid is alcohol. Histamine and alcohol share metabolic pathways that use the enzymes, aldehyde dehydrogenase and aldehyde oxidase.

Alcohol always releases histamine from your mast cells but if you develop to histamine sensitivity, this reaction become more prominent. You’ve probably seen this reaction before, it’s what makes a person’s face become flushed from drinking too much. Not only does alcohol release histamine, it also blocks to DAO. This histamine release in response to alcohol can get worse and worse.

The available information on histamine related issues has exploded in just the last two to three years. We are learning a lot more about histamine and DAO at a fast rate and this will only continue to get better.