Diamine oxidase (DAO) is a digestive enzyme that rids your body of histamine. Histamine is a signal protein important for digestion, allergic response, immunity, and more. Experts don't agree, but histamine intolerance (HIT) may happen after too much histamine builds up in your body.
Fermented foods can raise the levels of histamine in your gut if you don't have enough diamine oxidase enzyme or it doesn't work well. The extra histamine can cause a group of symptoms that mimic an allergic reaction called histamine intolerance.
Some experts think that HIT affects about 1 to 3 people out of 100. According to the American Academy of Allergy, Asthma, and Immunology, HIT isn't recognized as a medical condition.
Exactly how HIT happens is still a mystery, but scientists continue to research diamine oxidase to find out. Discover more about the diamine oxidase enzyme, if supplements can help, and other ways to treat your histamine-related symptoms.
What Is Histamine?
Histamine is a signal protein that comes from:
- Mast cells, a type of white blood cell in your tissues
- Basophils, a type of white blood cell in your blood
- Your gut
- Lymph nodes
- Thymus
- Fermented foods and drinks
What does histamine do?
Histamine is a key signal protein that can cause symptoms to help protect or maintain your body's health.
Histamine can help your:
- Immune system
- Allergic response
- Digestion
- Cardiovascular health (heart and blood vessels)
- Sleep
- Appetite control
- Brain health
- Body temperature
What Causes Histamine Intolerance?
Doctors don't know a lot about histamine intolerance, but some think extra histamine from certain foods can cause symptoms.
Also called food histaminosis or enteral histaminosis, HIT happens after your diamine oxidase enzyme gets out of balance.
Unbalanced DAO enzyme levels may happen because you have:
- Gene changes
- Medication interactions
- Specific medical conditions
One study reported that gut germs may also play a role in HIT. The small study found more kinds of healthy gut germs in people who didn't have HIT compared to people who did.
What are the symptoms of histamine intolerance?
With HIT, you may get allergy-like symptoms such as:
- Flushing
- Itchy skin
- Migraine or headache
- Nausea, vomiting, or gut issues
- Diarrhea
- Skin conditions
Is histamine intolerance the same as an allergic reaction?
No, it's not an allergic reaction or a food allergy. But HIT may mimic some of the same symptoms of allergy. That's why HIT is also called a "pseudoallergy."
When to call the doctor
Because HIT symptoms can mimic a life-threatening allergic reaction, it can be hard to tell the difference.
Get medical help right away if you get:
- Swelling in your face, eyes, lips, or throat
- Skin rash or hives
- Wheezing or trouble breathing
- Nausea, vomiting, or diarrhea
- Dizziness or fainting
What Is Diamine Oxidase (DAO)?
Diamine oxidase (DAO) is a working protein called an enzyme that uses copper to quickly break down histamine. Most DAO is found in your gut and kidneys. But the DAO supplement that you buy comes from pig (pork) kidney or pea shoots.
It can be hard to test for the enzyme and measure DAO in a lab. Without a reliable test, it's harder for doctors to detect low levels and diagnose HIT.
Talk to your doctor before taking DAO supplements to find out what's best for your health.
What Are the Benefits of Diamine Oxidase Supplements?
Diamine oxidase supplements claim to restore your DAO enzyme levels to get rid of histamine.
A few limited studies claim that DAO supplements can help ease your:
- Headaches
- Stomach problems
- Skin reactions
Only a few, small studies showed benefit with a few DAO brands for a short time. So doctors still aren't sure how well DOA supplements really work or how safe they are for long-term use.
Migraines and headaches
In one study, a few people with migraines took DAO supplements for over one month. They claimed it helped shorten their migraine attack time by almost 90 minutes.
Digestive symptoms
In a very small study, people with histamine intolerance who took DAO supplements said at least one digestive symptom got better.
In another small study, people taking DAO supplements for four weeks reported fewer HIT symptoms and less intense digestive symptoms.
Skin conditions
In one small, controlled study, people with chronic hives who took DAO supplements were able to lower their antihistamine medication dose.
But in another study, taking supplements and eating a low-histamine diet didn't help.
Are DAO Enzyme Supplements Safe?
Using DAO supplements for a short time appears safe for most people, but only limited safety studies have been done.
Keep in mind that dietary supplements aren't approved by the FDA, so aren't made under strict rules like medicines.
In fact, one review found that some batches of pork kidney DAO supplements can be about 10 times more active than others.
And using the supplement longer than a month may cause:
Symptom changes
Hypersensitivity
Dependence on DAO supplement
Allergic reactions from animal proteins (pig kidney)
Allergic reactions from plant proteins (pea shoots)
Who should consult a doctor before taking DAO supplements?
Because DAO supplements can contain tiny amounts of copper, plant, and animal proteins, always ask your doctor before taking the enzyme.
You may want to avoid DAO if you have:
- Wilson's disease
- Allergies to pork or animal proteins
- Religious or diet restrictions for pork
- Copper metabolism problems
- Are pregnant
- Kidney disease
- Mast cell activation disorder
- Take certain medicines such as NSAIDs, MAOIs, blood pressure, or antimucus meds
- Mastocytosis
- Chronic rash (urticaria)
Alternatives to Diamine Oxidase Supplements
Treatment for histamine intolerance usually starts with a low-histamine diet. You'll talk with your doctor and dietitian about:
Healthy foods to add
Avoiding higher histamine foods
Which foods trigger histamine
In a few small clinical studies, between 33% and 100% of people said a low-histamine diet helped ease their symptoms.
But in a few studies, there was no change in DAO enzyme activity after eating a low-histamine diet. So the complex link between DAO and histamine is still unclear.
Talk to your doctor or dietitian before you eliminate foods; they can help you decide what may be causing your symptoms.
What foods have higher histamine levels?
Some high-histamine foods include:
- Wine
- Beer
- Aged cheese
- Sauerkraut
- Canned fish
- Canned legumes
- Cured meats
- Dried sausages
- Dried fruit
- Avocado
- Eggplant
- Spinach
- Squash
- Tomato
- Oily fish
What foods trigger higher histamine levels?
These foods can trigger higher histamine in your body:
- Nuts (walnuts, cashews, and peanuts)
- Milk and yogurt
- Fish
- Pork
- Mushrooms
- Chocolate
- Shellfish
- Wheat
- Soy
- Pickled foods
- Citrus fruits such as strawberries and pineapples
- Carbonated drinks
How do I increase my DAO levels naturally?
Although nothing can really raise your DAO levels naturally, eating a balanced diet rich in vitamins can help.
Here are a few things you can do to promote healthy DAO levels:
Vitamin-rich diet. Eat foods to support your DAO enzyme, such as:
- Copper, zinc, and iron: Eat whole grains, sweet potatoes, chicken, and potatoes.
- Vitamin B6: Try oats, tuna, and rice.
- Vitamin C: Eat peppers, broccoli, and Brussels sprouts.
- Phosphorus and magnesium: Try turkey, eggs, and dark leafy greens.
Healthy fats. Omega-3 is an essential fatty acid that helps lower inflammation and supports your immune system. Be sure to get enough EPA and alpha-linolenic acid by eating salmon and eggs.
Takeaways
Diamine oxidase (DAO) supplements are usually added to a low-histamine diet to treat allergy-like symptoms that can show up if your DOA enzyme can't break down the extra histamine in foods --- a proposed condition called histamine intolerance (HIT). It's hard to know if you're having HIT or a serious, life-threatening allergy. So, if you get swelling, hives, wheezing, nausea, diarrhea, or dizziness, get medical help right away.
Diamine Oxidase FAQs
How long does it take for DAO supplements to work?
It usually takes about a month for DAO supplements to work, but talk to your doctor about your specific medical condition.
What depletes the DAO enzyme?
Although many things can deplete your DAO enzyme, lower levels have been reported with:
- Phlegm-lowering medication
- Antinausea medicine
- Alcohol
- Black tea
- Mate tea
- Energy drinks
Does green tea block DAO enzymes?
Although fermented tea can block DAO enzymes, green tea isn't fermented. Some studies show that green tea may actually block histamine. And this can help promote healthy DAO enzyme levels.
Can other supplements help block histamine?
Although there isn't a supplement to directly block histamine, there are some that may lower inflammation. Quercetin and bromelain are called mast cell stabilizers and may block histamine. Always talk to your doctor before taking any supplement and find out if it's safe for your health.
