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.