What is histamine?

 From Wikipedia:

“Histamine is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological function in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Histamine is involved in the inflammatory response and has a central role as a mediator of itching. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues.”

Histamine Intolerance (HIT) is an overaccumulation of histamine in the body. The term histamine intolerance is misleading as we all need histamine to defend our bodies against invasion by disease-causing agents. Histamine is produced by mast cells to fight against bacteria, infections, regulate our hormones, and run our digestive systems. Some people have too many mast cells, allergies or too little of the histamine-lowering enzyme diamine oxidase (DAO) causing the symptoms detailed below. Histamine is also present in foods such as tomatoes, avocados and citrus fruits, among others.

Individuals with HIT have higher levels of histamine in their bodies leading to certain symptoms. Histamine intolerance is projected to impact only 1% of the population but may people remain undiagnosed. Some people may have mastocytosis or mast cell activation disorder (MCAD) but because these are relatively new diseases, you may struggle to get a diagnosis from your doctor.

What are the symptoms?

While everyone’s histamine reactions vary from person to person, here is a list of some of the most common symptoms.

  • Headaches / migraines

  • Nasal congestion, sneezing, watery eyes

  • Hives / Itchy skin / Flushing / Dermatographism

  • Fatigue

  • Anxiety

  • Difficulty regulating body temperate (feeling cold or hot often)

  • Abnormal menstrual cycle

  • Hypertension

  • Digestive issues / abdominal cramps

What causes high histamine levels?

  •  Allergies

  • Bacterial overgrowth (SIBO)

  • Diamine Oxidase deficiency

  • Leaky gut

  • Gastrointestinal bleeding

  • Foods high in histamine

How it is treated

  • Antihistamines

  • Supplements

  • Low-histamine diet

  • DAO food supplements

How to test for HIT / MCAD

Your doctor can take a blood test to determine the ratio of histamine to DAO in your blood or test if serum tryptase is elevated which may indicate MCAD. However, these tests are not particularly reliable as both histamine and DAO levels can fluctuate wildly in your body at any given time. Unfortunately, because histamine intolerance is so tricky to test, food elimination can be the most effective way to find out if you have a histamine disorder.

If you have some of the symptoms listed above, please speak with your doctor about getting tested. The first step is figuring out what you have and then determining the treatment method that works best for you.