Your body has an enzyme called diamine oxidase (DAO) that breaks down histamine, a chemical that can cause headaches, stomach problems, and allergy-like reactions when it builds up too much. When you don’t have enough DAO, you may develop histamine intolerance. Scientists reviewed all the latest research to understand how DAO works, why some people don’t have enough of it, and whether taking DAO supplements can help. They found that genes and diet both affect how much DAO your body makes, and supplements show promise—but doctors still need better ways to diagnose the problem and improve how supplements work.

The Quick Take

  • What they studied: How an enzyme called diamine oxidase (DAO) helps your body handle histamine, what happens when you don’t have enough of it, and whether taking DAO supplements can help people feel better
  • Who participated: This was a review of existing research, so scientists looked at many different studies instead of testing new people themselves
  • Key finding: DAO is crucial for breaking down histamine in your body. When DAO levels are low, histamine builds up and causes problems like migraines, stomach issues, and allergy-like symptoms. Taking DAO supplements may help, but results vary between people and more research is needed
  • What it means for you: If you have unexplained migraines, digestive problems, or allergy-like symptoms, histamine intolerance might be worth exploring with your doctor. DAO supplements exist, but they’re not a guaranteed fix yet, and you should talk to a healthcare provider before trying them

The Research Details

This is a review article, which means scientists gathered and analyzed all the existing research on diamine oxidase and histamine intolerance instead of conducting their own experiment. They looked at studies about how DAO works in your body, what genetic and dietary factors affect DAO levels, clinical trials testing DAO supplements, and current challenges in diagnosing and treating histamine intolerance.

By reviewing many studies together, scientists can see patterns and understand the big picture of what we know and don’t know about DAO deficiency. This type of research is helpful for identifying gaps in our knowledge and pointing out where future research should focus.

The researchers examined both the biological mechanisms (how DAO actually works) and practical treatment approaches (like supplements) to give a complete overview of the topic.

Review articles are important because they help doctors and patients understand what the current evidence actually shows. Instead of looking at one small study, a review pulls together information from many studies to see what’s consistently true. This helps identify which treatments really work and which ones need more testing. For histamine intolerance, this is especially important because it’s not well understood and there’s no standard way to diagnose it yet.

This review was published in a scientific journal, which means other experts reviewed it before publication. However, since this is a review of other studies rather than original research, its strength depends on the quality of the studies it examined. The review acknowledges important limitations in the field, including lack of standardized diagnostic methods and gaps in how well supplements work. Readers should note that this reflects the current state of the science—the field is still developing better tools and treatments.

What the Results Show

Diamine oxidase (DAO) is an enzyme your body uses to break down histamine, a chemical messenger involved in many body functions. When DAO doesn’t work properly or you don’t have enough of it, histamine builds up to harmful levels, causing a condition called histamine intolerance.

The review found that both your genes and your diet affect how much DAO your body produces. Some people are born with genes that make less DAO, while others may have low DAO because of diet, medications, or other health conditions. This explains why histamine intolerance affects different people in different ways.

DAO supplements exist and show promise in helping some people with histamine intolerance feel better. However, the review found that these supplements don’t work equally well for everyone, and scientists still don’t fully understand why. The supplements come from different sources (like pea sprouts or kidney beans), and these differences may affect how well they work.

The researchers identified major challenges that are slowing progress: doctors don’t have a standard, reliable test for histamine intolerance, supplements vary in quality and effectiveness, and there are no clear government regulations for DAO supplements.

The review found that histamine intolerance can cause a wide range of symptoms beyond just migraines and stomach problems. People may experience allergy-like reactions, skin issues, and other symptoms that can be confused with food allergies or other conditions. This makes diagnosis tricky because the symptoms overlap with many other health problems.

The research also showed that certain foods high in histamine (like aged cheeses, fermented foods, and processed meats) can make symptoms worse in people with DAO deficiency. This suggests that dietary changes might help alongside or instead of supplements for some people.

Additionally, the review noted that some medications and health conditions can lower DAO levels, meaning histamine intolerance might develop later in life rather than being something you’re born with.

This review builds on earlier research by bringing together the latest findings about DAO and histamine intolerance. Previous studies focused mainly on understanding how DAO works in the body. This review goes further by examining both the science and practical treatment options like supplements. It also highlights that while scientists have known about DAO for a long time, histamine intolerance is still not well recognized by many doctors, and treatment options remain limited compared to other digestive or allergy conditions.

The biggest limitation is that this is a review of existing research, not a new study with participants. The quality of the conclusions depends on the quality of the studies reviewed. The review found that many existing studies on DAO supplements are small and don’t follow strict scientific standards, making it hard to draw firm conclusions.

Another major limitation is that there’s no standard way to diagnose histamine intolerance, so different studies may be looking at different groups of people. This makes it difficult to compare results across studies.

The review also notes that most research on DAO supplements is relatively new, so we don’t have long-term data on whether they’re safe and effective over months or years. Additionally, most studies have been done in specific populations, so results may not apply equally to everyone.

The Bottom Line

If you have persistent migraines, digestive problems, or allergy-like symptoms that don’t fit typical allergies, ask your doctor about histamine intolerance. While there’s no perfect test yet, your doctor can help evaluate whether it might be your problem. Try keeping a food and symptom diary to see if certain foods trigger your symptoms (moderate confidence—this is helpful but not definitive). If histamine intolerance seems likely, talk to your doctor or a dietitian about trying a low-histamine diet first, as this has fewer risks than supplements (moderate confidence). DAO supplements may help some people, but results vary widely, so discuss with your doctor whether they’re worth trying and which type might work best for you (low to moderate confidence—more research is needed).

This research matters most for people who have unexplained migraines, chronic digestive problems, or allergy-like reactions that don’t respond to typical allergy treatments. It’s also relevant for people with certain digestive conditions (like IBS) that might be partly caused by histamine intolerance. Healthcare providers, especially those treating headaches, digestive issues, or allergies, should be aware of histamine intolerance as a possible diagnosis. People should NOT assume they have histamine intolerance just because they have headaches or stomach problems—many other conditions cause these symptoms, and a doctor should help figure out what’s actually going on.

If you try dietary changes (avoiding high-histamine foods), you might notice improvement in symptoms within 1-2 weeks, though it can take longer for some people. If you try DAO supplements, give them at least 2-4 weeks to see if they help, since your body needs time to adjust. However, if supplements don’t help after a month or two, they probably won’t work for you. Long-term management usually involves a combination of diet changes and possibly supplements, with ongoing adjustments based on how you feel.

Want to Apply This Research?

  • Track daily symptoms (headaches, digestive issues, skin reactions) on a 1-10 scale and note which foods you ate that day. After 2-3 weeks, look for patterns between specific foods and symptom flare-ups. This helps identify your personal histamine triggers.
  • Start a low-histamine diet by eliminating one high-histamine food group at a time (like aged cheeses or fermented foods) for one week and track whether symptoms improve. Once you identify your trigger foods, you can avoid them while still eating a balanced diet.
  • Use the app to maintain a 4-week food and symptom log before trying supplements, then continue logging for 4 weeks after starting supplements (if you choose to try them). Compare the two periods to see if supplements actually help your specific symptoms. Share this data with your doctor to guide treatment decisions.

This review summarizes scientific research about diamine oxidase deficiency and histamine intolerance, but it is not medical advice. Histamine intolerance is not yet recognized as a standard diagnosis by all medical organizations, and there is no universally accepted test for it. If you experience persistent migraines, digestive problems, or allergy-like symptoms, consult with a qualified healthcare provider for proper evaluation and diagnosis. Do not start DAO supplements or make major dietary changes without discussing them with your doctor first, as they may interact with medications or affect other health conditions. The effectiveness of DAO supplements varies between individuals, and more research is needed to understand how well they work. This information is current as of the review publication date but may change as new research emerges.