DAO and Histamine

Purity Carr
Aug 22
2 min read

Many people are familiar with histamine when it comes to allergies, but histamine also plays an important role in digestion, immune response, and even hormone balance. Problems arise when histamine builds up in the body faster than it can be broken down. This is where DAO (Diamine Oxidase) becomes important.

What is DAO?

DAO is the main enzyme in the gut responsible for breaking down histamine from food before it is absorbed into the bloodstream. It acts as the body’s first line of defence against excess histamine coming in through the diet.

Where does DAO come from?

DAO is made in the cells lining the small intestine and is also produced in the kidneys and placenta. In the gut, it is released especially during digestion to help protect the body from too much histamine entering circulation.

What does DAO do?

DAO breaks down histamine into an inactive compound called imidazole acetaldehyde. This compound is then further metabolised and excreted. By doing this, DAO helps lower the total histamine load and prevents histamine from accumulating in the bloodstream.

Why does DAO matter?

When DAO levels are low, histamine is not cleared efficiently. This can happen due to genetics, gut inflammation, certain medications, or deficiencies in key nutrients. If histamine builds up, it may trigger symptoms such as:

Headaches or migraines
Flushing or skin redness
Bloating and digestive discomfort
Hives or rashes
Palpitations
Worsening of menopausal or allergy-like symptoms

How to support DAO activity

There are practical ways to support your body’s DAO levels and reduce histamine symptoms:

Eat fresh foods rather than leftovers, as stored and processed foods contain higher histamine.
Ensure adequate intake of nutrients that support DAO activity, especially vitamin B6, copper, and vitamin C.
In some cases, DAO supplements can be taken with meals to help break down histamine before it enters circulation. These are usually derived from porcine kidney and are intended as digestive support.

Final thoughts

DAO is a key enzyme in controlling the balance between histamine intake and clearance. For individuals who experience symptoms of histamine intolerance, paying attention to food freshness, nutrient support, and in some cases supplementation can make a meaningful difference.