Linking allergies & histamine

Updated: Aug 4, 2021

Allergies are considered one of the fastest growing chronic diseases in Australia. More than 20% of the population in industrialised countries suffer from a food intolerance or allergy.

Symptoms of allergic disease can range from allergic rhinitis, hay fever, digestive disorders, eczema and asthma, or life-threatening anaphylaxis.

I am going to run you through what allergies & intolerances are, how to identify and treat them.

Understanding Allergies

Allergies occur when our immune system reacts to proteins in the environment that are harmless for most people, such as house dust mites, pets, pollen, other insects, moulds and foods.

An intolerance is considered a “chemical” reaction to a substance, most often food, and will not show up on a traditional allergy test.

The term sensitivity is less clear, however in complementary medicine it is commonly understood as a delayed and milder reaction.

The possible manifestation of a food reaction is widespread and non-specific. They have been linked to gastrointestinal symptoms, skin conditions, respiratory issues, fatigue, headache, migraine, cognitive deficits, neurodevelopmental disorders, anxiety, depression, joint pain, muscle pain, and endocrine disturbances. Regardless of the cause, be it environmental or food-induced, the impact on an individual’s quality of life can be considerable.

What is Histamine?

Histamine is a chemical compound that is involved in the immune system response. It is often associated with seasonal allergies, food allergies and symptoms such as headaches, nasal congestion, sneezing and difficulties with breathing.

Sometimes you may experience symptoms that aren’t associated with the environment, such as a runny nose, sneezing, and itching after wine or certain foods like bananas, avocados, or tomatoes.

Histamine acts like a bouncer in a club. It helps your body get rid of something that’s bothering you, in this case, an allergy trigger or “allergen”.

Histamine plays an important role in helping the body communicate with the brain, alert the immune system to a potential threat, and launch an inflammation response.

What is a histamine intolerance?

Histamine intolerance occurs when there is a build-up of histamines in the blood stream and the body is no longer able to break it all sufficiently.

Typical symptoms of histamine intolerance include:

o Gastrointestinal upset, including altered bowel function, abdominal pain and nausea

o Headaches, dizziness and migraines

o Joint pain

o Hives and flushing skin rashes

o Tissue swelling

o Brain frog, anxiety and depression

o Congestion, runny nose, sneezing and difficult breathing

o Menstrual changes, fluid retention, PMS with mood changes

What are the causes of histamine intolerance?

There can be many reasons for an increase of histamine. Medications, certain medical conditions, nutritional deficiencies, environmental factors and diet can all be potential factors in the development of histamine intolerance.

However, the three most common causes include genetic abnormalities, bacterial overgrowth and high estrogen levels.


Genetics plays a major role in how well your body breaks down histamine. According to Gene Ontology, proteins and enzymes encoded by more than 200 genes are involved in the histamine pathway. However, the key genes responsible for maintaining the physiological level of histamine are HDC, Aoc1 (DAO) and HNMT.

HDC The histidine decarboxylase enzyme (HDC) is the sole member of the histamine synthesis pathway. Histamine cannot be generated by any other known enzyme.

DAO Diamine oxidase (DO) is one of the major enzymes that breaks down histamine. DAO is mostly found in the gut, though it can also be found in the kidney and connective tissues. Because of its presence in the gut, this enzyme is our primary defense against histamine and histamine-producing bacteria in our food.

HNMT Histamine N- Methyltransferase (HNMT) is an enzyme expressed in the central nervous system that works throughout the body to metabolise the histamine created by your body by deactivating it and breaking it down so it no longer triggers a physiological response.

Bacteria overgrowth

SIBO and dysbiosis, which are both characterized by an overgrowth of bacteria, are often likely to be found at the root of a histamine intolerance. Some bacterial strains are more likely to produce histamine, therefore an overgrowth of these strains can promote more reactivity and histamine intolerance symptoms. If you suspect you have SIBO read up on it here.