What Are Histamines?
Most people have heard of antihistamines, the allergy medications, but fewer know what histamines do. Histamines are natural chemicals produced by the immune system. They help the body respond to allergens—substances like pollen, dust, or pet dander—by triggering sneezing, itching, or tearing. This reaction protects the body from potential threats.

Sometimes, however, histamines overreact. They can treat harmless substances as dangers, leading to allergy-like symptoms. That’s where antihistamines come in—they suppress this overreaction.

What Is Histamine Intolerance?
Histamine intolerance shares symptoms with allergies but can affect other bodily functions as well. Signs vary depending on the individual, but common symptoms include:

Digestive problems

Fatigue

Headaches or migraines

Heartburn

Hives

Irregular menstrual cycles

Nausea

Sinus issues and congestion

Watery eyes

Vomiting

Severe cases may include:

Abdominal pain

Anxiety

Difficulty breathing

Dizziness

High blood pressure

Irregular heart rate

Trouble regulating body temperature

Swollen tissues

What Causes Histamine Intolerance?

Histamine intolerance doesn’t mean the body cannot handle histamines; it means the body has too much. Histamines perform several key functions, including aiding digestion by releasing stomach acid and sending signals to the brain.

The enzyme diamine oxidase (DAO) normally breaks down histamine during digestion. A DAO deficiency prevents this process, leading to excess histamine in the body. DAO deficiencies can be caused by:

Gastrointestinal disorders

Medications that interfere with DAO production

Histamine-rich foods

Foods that trigger histamine release

Foods that block DAO enzymes

Bacterial overgrowth in the gut

Kerry Torrens, BSc, explains: “Histamine intolerance is unlike other allergies. It’s not a reaction to histamine itself but to the fact that the body contains too much of it. Everyone has a personal ‘histamine bucket.’ Once it overflows, symptoms appear.”

Managing Histamine Levels with Diet

Diet plays a major role in managing histamine intolerance. Certain foods can increase histamine or block DAO enzymes. These include:

Alcohol and fermented foods

Black tea, green tea, energy drinks

Fruits like avocados, bananas, papaya, dried fruits, and citrus

Vegetables like eggplant, spinach, and tomatoes

Beans and nuts

Processed or smoked meats

Shellfish

Aged cheese

Chocolate

Food dyes and additives

There’s no permanent “histamine-free” diet. Work with a dietitian to find a plan that works for you. Focus on low-histamine foods such as:

Gluten-free grains (rice, quinoa)

Non-citrus fruits (avoid avocado and bananas)

Most vegetables (excluding eggplant, spinach, and tomatoes)

Eggs

Dairy substitutes like almond milk

Fresh meat and fish

Cooking oils like olive oil

Diagnosis and Treatment

If you suspect histamine intolerance, don’t self-diagnose. Symptoms resemble allergies, infections, or other disorders. A doctor may:

Recommend an elimination diet for 14–30 days

Slowly reintroduce foods to test reactions

Conduct a blood test for DAO deficiency

Antihistamines can help relieve symptoms but do not reduce the body’s histamine load. They provide temporary relief but are not a complete solution.