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What are histamines?

Does a tasty plate of Eggs Benedict send you into a sneeze spiral? Do you often find yourself with red and itchy skin? Well, it looks like you are not alone! According to the Asthma and Allergy Foundation of America, more than 50 million Americans experience some type of allergy every year. Hay fever, food allergy, skin allergy are very common in the United States.

People living with allergies are no strangers to 'antihistamines.' What are antihistamines, and how do they help manage your allergies? To understand that, let's first look at histamine. Histamine is generally our body's ally.

A few of the many functions it performs are contraction of smooth muscles, acid secretion in the stomach, stimulation of the brain to keep it active, and lowering our blood pressure.

Histamines and allergies

Histamine is released by the immune cells when you come in contact with possible allergens. This generally protects your body from allergic reactions.  

Sometimes, the immune cells release histamine in response to components in the environment or food that are harmless. In other words, the immune system mistakes a non-allergen for an allergen and mounts an allergic reaction.

This overreaction leads to watery eyes, nasal congestion, swelling, itching, vomiting, or diarrhea. In severe cases, your airways may swell, and enough oxygen cannot be supplied to your organs. It can at times even be fatal when it leads to an anaphylactic shock. This needs to be treated with an 'EpiPen' immediately. EpiPen is basically an injection of epinephrine to treat your severe allergic reaction instantly.

What is histamine intolerance?

Antihistamines are used to treat mild to severe allergy symptoms. They act by blocking the effect of histamine, hence the name ANTIhistamines.

So, why do some people react so badly to the build-up of histamine?

This is all thanks to a condition called HISTAMINE INTOLERANCE. This condition either causes a rapid build-up of histamine in the body and/or results in an inability to break down histamine effectively.

An enzyme called diamine oxidase, DAO for short, is responsible for breaking down histamine. Lower levels of this enzyme result in histamine intolerance. A few factors that influence the DAO enzyme levels include conditions like inflammatory bowel disease, medications that block DAO action, and certain histamine-rich foods that cause DAO dysfunction.

AOC1, or Amine Oxidase Copper Containing 1, is a major genetic contributor to histamine intolerance. This gene is responsible for the production of the DAO enzyme.  If you carry a ‘faulty’ version of the AOC1 gene, then less DAO is produced, leaving you highly prone to allergic reactions. 

what is histamine intolerance

Histamine intolerance can be treated by following a low histamine diet and taking DAO supplements. 

Histamine intolerance genetic test

A simple genetic test can help identify your risk for histamine intolerance.

It involves analyzing what version or variant of the AOC1 gene you carry. 

Most genetic ancestry tests provide your DNA information in the form of a text file called the raw data.  This typically looks like a bunch of numbers and letters that can be decoded to obtain useful health information. This is where Xcode Life comes into play.

All you have to do is upload this file and order any of the 13 in-depth health reports. The AOC1 gene for histamine intolerance is analyzed as a part of the Gene Allergy report.  It also includes various seasonal and environmental allergies. 


What Is Food Intolerance?

Food intolerance or food sensitivity describes the difficulty in digesting certain foods and can lead to unpleasant reactions like intestinal gas, abdominal pain, or diarrhea. 

The symptoms of food intolerance appear only after a few hours of consuming the food. 

It can be difficult to identify food intolerance as the symptoms are often mistaken for other conditions. 

Some common symptoms of food intolerance include:

Food intolerances aren’t life-threatening. However, they can be very problematic for those affected.

Some causes of food intolerance are the absence of certain digestive enzymes (proteins that help with the digestion of food), some chemicals/additives in the food, and toxins.

Common food intolerances seen in people are:

  1. Lactose intolerance: Inability to digest a protein, lactose, found in dairy products
  2. Gluten intolerance: Inability to digest a protein, gluten, found in barley, wheat, and rye
  3. Caffeine intolerance: Inability to digest a chemical, caffeine, found in beverages like coffee and tea

What Is The Difference Between A Food Allergy And Food Intolerance?

While food intolerance is a problem with digesting food, food allergies are due to our immune system reacting to the food item itself. 

Food allergy occurs when the immune system sees a specific component in the consumed food as an “enemy” to the body and sends out a response that results in allergic reactions. 

The symptoms of food allergy occur soon after eating the food and are much more severe than those seen in the case of food intolerances. 

In rare cases, food allergies can result in a reaction called ‘anaphylaxis’ where your blood pressure drops and your airway narrows down - this can potentially be life-threatening. 

Introduction to Mushroom Intolerance 

Mushrooms are loved worldwide as they contain flavor enhancers and are a gourmet’s delight. This makes them the most popular choice for pizza topping, after pepperoni! 

Some nutritional facts about mushrooms

Mushrooms are a “powerhouse of nutrition” and not a white food to be avoided. 

Some research studies show that they can be used to lower the risk of diseases such as cancer, Alzheimer’s, and Parkinson’s.

The Genetic Basis of Mushroom Intolerance

OCTN1 Gene

Also known as SLC22A4, this gene is located on the long arm or the q arm of chromosome 5.

Chromosomal location of OCTN1 gene.
Chromosomal location of OCTN1 gene.

OCTN1 produces a protein that is responsible for the transport of positively charged compounds - in this case, ergothioneine - a substance present at high levels in mushrooms.

A study established an association between the OCTN1 gene and mushroom intolerance risk. 

This interaction was observed among patients with Crohn’s disease.

Crohn’s falls under a group of diseases (called the inflammatory bowel diseases) that affect the digestive tract - the mouth, esophagus, stomach, small intestine, and large intestine. Crohn’s results in the inflammation or swelling of the digestive tract, which can lead to side effects like stomach pain, diarrhea, and weight loss. 


rs1050152 of the OCTN1 gene has an association with mushroom intolerance. In a study conducted in the New Zealand population, among the people who were mushroom intolerant, it was found that the T allele of rs1050152 was present in a higher number (in people with and without Crohn’s disease). This suggests that having a T allele in rs1050152 can increase your risk for mushroom intolerance. 

rs1050152 was previously found to be associated with a risk for Crohn’s disease.

Shiitake Mushroom Intolerance

The shiitake is an edible mushroom native to East Asia. Shiitake mushroom intolerance is one of the most common forms of mushroom intolerance.

The American chemical society in 2005 stated that mushroom contained the highest concentrations of ergothioneine, higher than either of the two dietary sources, wheat germ and chicken liver - which were previously believed to contain the most.

When compared with the other types of mushrooms cultivated in the US, the shiitake variety contained the highest amount of L-ergothioneine, which explains why shiitake mushroom intolerance is more common.

Sudden Mushroom intolerance

There have been reported instances of people developing sudden mushroom intolerance, without any prior incidents.

This could either be due to the type of mushroom consumed or a mushroom allergy.

The best way to find out is to take up a food intolerance test.

Risk Factors For Mushroom Intolerance

People at high risk for mushroom allergy include:

Remedies For Mushroom Intolerance

The best and the only way to avoid mushroom intolerance is to remove mushrooms from the diet completely. 

The available study on the reason behind mushroom intolerance identified ergothioneine as the ‘component’ that leads to intolerance. So, it is also important to be wary of foods containing ergothioneine. Foods high in ergothioneine include:



Updated 13th March, 2021

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