Histamine intolerance and the DAO gene – it is an enzyme issue, not an allergy
Some people carry genetic polymorphisms on the DAO gene (Diamine Oxidase).
This does not mean there is something “wrong” with you. It simply means your body may produce less of the DAO enzyme, or the enzyme may work more slowly. This can increase your risk of developing histamine intolerance.
It is important to understand that histamine intolerance is not a food allergy. It is most often an enzyme deficiency issue.
You can think of it like this: your body is exposed to histamine every day, from food, from your gut bacteria and from your own immune system.
If your body cannot break histamine down efficiently, it can build up and trigger symptoms.
What Is The DAO Enzyme
DAO (Diamine Oxidase) is the main enzyme that breaks down histamine in the gut.
Its role is to:
break down histamine coming from foods
prevent excess histamine from being absorbed into the bloodstream
protect the body from histamine overload
When DAO activity is low, histamine from food is more likely to pass into circulation and contribute to symptoms.
This is why people with slow DAO genes often notice symptoms after eating, rather than immediately on contact like a true allergy.
DAO Gene Polymorphisms Do Not Mean You Will Definitely Have Symptoms
Your genetics show your tendency, not your destiny.
However, if your DAO gene is slow, your ability to clear histamine is already reduced.
If this is combined with gut inflammation, nutrient deficiencies, stress, medications or alcohol, histamine symptoms can become much more noticeable.
What Nutrients Act As Co-Factors For DAO
Like all enzymes, DAO requires specific nutrients to work properly.
Key co-factors that support DAO activity include:
Vitamin B6 – essential for DAO enzyme function
Copper – required for the catalytic activity of the DAO enzyme
Vitamin C – supports histamine breakdown and reduces circulating histamine levels
Zinc – supports gut lining integrity and enzyme activity
Iron – low iron has been linked to reduced DAO activity
If these nutrients are low, DAO activity may be further reduced, even if the gene itself is only mildly slow.
Alcohol Strongly Inhibits DAO
Alcohol is one of the most powerful blockers of DAO.
It will:
directly inhibits DAO enzyme activity
increases histamine release
increases gut permeability, allowing more histamine to enter the bloodstream
For people with slow DAO genes, alcohol often becomes a major trigger for symptoms such as:
flushing
headaches or migraines
nasal congestion
palpitations
anxiety or a “wired” feeling
Even small amounts of alcohol can significantly reduce histamine clearance.
Why A Low Histamine Diet Is Often Helpful With Slow DAO Genes
When DAO activity is reduced, lowering the amount of histamine coming in from food can be very helpful.
A low histamine diet does not need to be permanent, but it can be extremely useful during periods of symptoms, gut healing or high stress.
Common high-histamine or histamine-releasing foods include:
aged and fermented foods (cheese, yoghurt, kefir, kombucha, sauerkraut)
cured and processed meats
leftovers stored for long periods
smoked fish and shellfish
tomatoes
spinach
avocado
eggplant
citrus fruits
chocolate
vinegar and soy sauce
bone broth cooked for long periods
alcohol
Reducing these foods temporarily can help lower the overall histamine load on the body.
Can DAO Supplements Be Helpful
For some people with slow DAO genes, DAO enzyme supplements taken before meals can be very helpful.
These supplements provide the DAO enzyme directly and can:
improve tolerance to moderate-histamine meals
reduce post-meal symptoms
support quality of life when eating out or travelling
They are not a cure, but they can be a useful short-term or situational support tool.
Summary: A Supportive And Balanced Approach
If you carry DAO gene polymorphisms, the goal is not to become fearful of food.
The goal is to:
lower the histamine load when symptoms are high
support the nutrients that your enzymes require
heal and protect the gut
reduce known inhibitors such as alcohol
use targeted support such as DAO supplements when appropriate
When the body is supported correctly, many people find their tolerance improves significantly over time.
Your genes show how your body prefers to be supported.
With the right co-factors and lifestyle strategies, you can help your DAO pathway work as efficiently as possible.
If you’re unsure about what works best for your body, it’s always worth discussing your symptoms and options with a healthcare practitioner.