Histamine is a natural compound in the body that plays a key role in the immune system, digestion, and brain function. However, when the body struggles to break down histamine properly, it can lead to histamine intolerance—a condition where histamine builds up and triggers various uncomfortable symptoms.
One of the most important enzymes responsible for breaking down histamine is diamine oxidase (DAO). When DAO enzyme activity is low, histamine is not cleared efficiently, leading to symptoms that can affect the skin, digestion, breathing, and even mood.
But what causes low DAO levels? The answer lies in a complex web of factors, including genetics, gut health, and environmental influences. While many people turn to low-histamine diets for relief, understanding the root causes of histamine intolerance can help create more personalised solutions beyond simply avoiding certain foods.
What Is Histamine and Why Does It Matter?
Histamine is found in certain foods, the gut, and immune cells. It plays several roles in the body, such as:
✅ Supporting immune responses to infections
✅ Helping with stomach acid production for digestion
✅ Acting as a neurotransmitter in the brain, influencing mood and sleep
Normally, histamine is broken down by enzymes like diamine oxidase (DAO), which is mainly found in the intestines, and histamine-N-methyltransferase (HNMT), which works in the liver. If these enzymes don’t work properly, histamine builds up and causes symptoms.
Symptoms of Histamine Intolerance
Histamine intolerance can cause a wide range of symptoms, which makes it hard to diagnose. Some of the most common include:
🔹 Skin issues: Rashes, hives, flushing, and itching.
🔹 Digestive problems: Bloating, diarrhoea, nausea, and acid reflux.
🔹 Respiratory symptoms: Nasal congestion, sinus issues, and shortness of breath
🔹 Headaches and migraines: Due to blood vessel dilation.
🔹 Fatigue and brain fog: Due to histamine’s effects on the nervous system.
🔹 Hormonal imbalances: Histamine and estrogen are closely linked, affecting menstrual cycles and PMS symptoms.
What Causes Low DAO Enzyme Activity?
1. Genetic Polymorphisms
Some people genetically produce less DAO enzyme, making it harder for their bodies to break down histamine. Genetic testing can reveal variations (or polymorphisms) in the AOC1 gene, which is responsible for DAO production. If you have this gene variation, you may be more prone to histamine-related issues.
2. Gut Health Issues
The DAO enzyme is produced in the small intestine. Leaky gut, dysbiosis (imbalanced gut bacteria), and inflammation can all damage the intestinal lining and reduce DAO production. Conditions like irritable bowel syndrome (IBS), Crohn’s disease, and SIBO (small intestinal bacterial overgrowth) are often linked to histamine intolerance.
3. Nutrient Deficiencies
Certain nutrients are needed for DAO enzyme function, including:
✅ Vitamin B6
✅ Copper
✅ Vitamin C
Low levels of these nutrients can impair DAO activity, making histamine breakdown less efficient.
4. High Histamine Foods & Alcohol
Some foods naturally contain high histamine levels, including:
- Fermented foods (yoghurt, sauerkraut, kombucha)
- Aged cheeses
- Cured meats
- Vinegar-based foods
- Wine and beer
Alcohol, especially red wine, blocks DAO activity, worsening symptoms.
5. Hormonal Imbalances (The estrogen-Histamine Connection)
Estrogen and histamine are closely linked, and high estrogen levels can increase histamine production while reducing DAO enzyme activity. This is why women often experience worse histamine symptoms before their period, during pregnancy, or while on the pill.
If the liver is not breaking down estrogen properly, it can lead to higher circulating histamine, causing headaches, allergies, and mood swings. Supporting liver detoxification and balancing estrogen levels can be an important part of managing histamine intolerance.
Beyond a Low-Histamine Diet: Personalised Solutions
Many people with histamine intolerance try a low-histamine diet, which can provide short-term relief but doesn’t address the root causes. Instead, a personalised approach using functional testing and targeted nutrition can help restore DAO activity and improve tolerance over time.
Here’s what that might look like:
1. Functional Testing
Testing can provide insights into gut health, genetic factors, and hormone imbalances. Some helpful tests include:
- Gut microbiome testing (to check for dysbiosis, SIBO, or leaky gut)
- Nutrient testing (for vitamin B6, vitamin C, and copper)
- Hormone testing (to assess estrogen levels and liver function)
2. Supporting DAO Production
Increasing DAO levels naturally can be achieved through:
- Gut healing protocols (probiotics, digestive enzymes, anti-inflammatory diets)
- DAO-supporting supplements (vitamin B6, copper, and DAO enzyme supplements)
- Reducing alcohol and processed foods
3. Managing Estrogen and Liver Health
Since excess estrogen can increase histamine, supporting liver detoxification can help, including:
- Eating cruciferous vegetables (broccoli, cauliflower, Brussels sprouts)
- Supporting liver function with milk thistle and dandelion root
- Avoiding synthetic oestrogens from plastics, skincare, and hormonal medications if possible
Final Thoughts
Histamine intolerance is more than just a reaction to food—it’s a complex issue involving gut health, genetics, and hormones. While avoiding high-histamine foods can help in the short term, long-term relief comes from addressing the root causes and improving DAO enzyme function.
With functional testing, gut healing, and hormone balancing, many people can improve their histamine tolerance and experience fewer symptoms without extreme food restrictions. A personalised approach can make all the difference in finding lasting relief and restoring balance to the body.
Check my services at Elemental Health and Nutrition to learn more!