Histamine intolerance is a theory that diet influences blood histamine and allergy-like symptoms in susceptible individuals.
Histamine toxicity (a type of food poisoning) is the basis of the theory. As food starts to spoil, the bacteria growing in it produce histamine which leads to allergy-like symptoms. The most common foods implicated in histamine toxicity outbreaks are scombroid species fish (such as tuna). Everyone that eats the spoiled fish will develop symptoms. Histamine intolerance is a theory that some people are more sensitive to dietary histamine and would experience symptoms with a diet that is generally tolerated. Typical symptoms include:
- Skin: itching, hives, flushing
- Respiratory: nasal and sinus congestion
- Digestive: gas, bloating, diarrhea, nausea
- Other: brain fog, fatigue, irritability, headache, rapid heart rate, blood pressure changes, etc.
Histamine intolerance is more likely if the individual experiences several typical symptoms, especially digestive. Histamine intolerance is less likely with just one symptom. There are two overlapping parts to the theory:
1) Low levels of diamine oxidase (DAO) enzyme: histamine in food is broken down in the digestive system by the diamine oxidase enzyme. If DAO is not working properly, the individual may be more likely to absorb dietary histamine.
2) Histamine releasing foods: Certain foods (such as egg white and strawberries) are suggested to release histamine in the digestive system which would then be absorbed into the body (especially with low levels of DAO).
If an individual is susceptible as described above, a diet low in histamine and histamine releasing foods will improve symptoms.
There is very little research to support the histamine intolerance theory.
There were some preliminary studies when the histamine intolerance theory was first proposed in Germany in the 1970’s/80’s, but there has been very little research since then. Dr. Janice Joneja (Immunology Ph.D. and Canadian dietitian) was one of the first health care professionals to translate this information and create English diet guidelines. I completed a Master’s of Science degree at the University of British Columbia (Dr. Joneja was one of my supervisors) in the mid-1990’s researching the Benefit of a Histamine Reducing Diet in Chronic Urticaria and Angioedema. In summary, around 20% of the low-histamine diet subjects had substantial symptom improvement, which is what we expected. Diet is one of many possible contributing factors to chronic urticaria (hives), so we did not expect everyone to improve. To my knowledge, there have not been any other studies looking specifically at a low histamine diet since this study in the 1990’s.
Most information on this topic is an educated guess.
Since there is very little research, most histamine intolerance information is opinion or speculation. For example, there is no research to support the concept of histamine-releasing foods. This theory is a possible explanation why some people experience allergy-like symptoms with specific foods, even though they don’t have a true allergy to the food. The theory was repeated over-and-over, and at some point, was assumed to be fact. As awareness of this concept spread on the internet, those suffering from symptoms started adding their problematic foods to the lists. The restricted food lists grew longer and longer. “Histamine-releasing foods” lists, should more appropriately be called “foods that have been reported to increase histamine-like symptoms.”
Currently, there is not an accepted diagnostic test for histamine intolerance.
Symptom improvement on a low histamine diet, diamine oxidase (DAO) supplementation or both is the only criteria for diagnosis. Essentially, it is a self-diagnosis.
Diet is one of many possible causes of typical histamine intolerance symptoms.
When someone has typical symptoms, they often assume they have histamine intolerance and need to follow a low histamine diet. However, many factors can contribute to the symptoms (e.g., seasonal allergy). Just because the symptoms sound like histamine intolerance, does not mean that a low histamine diet is necessary. The only way to know is to trial a low histamine diet. Additionally, there are claims that a low histamine diet will lower total body histamine, which may be true for individuals with reduced ability to break food histamine down (e.g., low DAO activity). However, excess histamine from a different source (e.g., seasonal allergies), will not improve with a low histamine diet.
Many people have reported symptom improvement with a low histamine diet, so a three-week dietary trial may be worthwhile.
Even though there is very little research to support the theory, many people have reported benefit. The good news is that symptoms will improve quickly if the diet is going to help. A common recommendation is a three-week trial. See The Practical Guide to the Low Histamine Diet for further information.