Histamine intolerance is a disorder in which histamine builds up in the body due to the inability to metabolize or break down histamine. The intake of high levels of histamine through the diet or the environment contributes to the wide range of symptoms associated with histamine intolerance. Although estimates show a small percentage of people with histamine intolerance (1), the relationships between histamine and histamine intolerance are worthy of examination for the sufferers who might benefit from a change in diet. If suffering from the symptoms of histamine intolerance, can following a low histamine diet help? What are the guidelines for the low histamine diet?
What is Histamine?
Histamine is a bioactive organic compound that can act as a hormone or neurotransmitter (chemical messenger in the nervous system). Histamines play a prominent role in the immune system as part of allergic responses and a driver of inflammation. Studies have shown that histamine can regulate immune responses, affect hormones, and impact digestive juices (2). Histamine also stimulates mucus production in the lungs and sinuses and aids in the contraction of smooth muscles in the gastrointestinal tract and airways.
Foods often provide histamines, and several common food items have high histamine levels. However, the body also makes histamine, as it provides numerous functions.
Many different types of cells synthesize histamine, including mast cells, platelets, and some neurons (1). Cells store histamine, releasing it when triggered by specific criteria, and are the driver behind many symptoms. For example, mast cells release histamine when triggered by repeated contact with allergens such as mold or tree pollens. In this case, histamine may cause sneezing, a runny nose, and a headache. Besides responding to allergens, histamine can be released upon experiencing cold temperatures, particular foods, medications, and even trauma (1).
Histamine Intolerance (HIT) – Impaired Ability to Break Down Histamine
The term “histamine intolerance” does not mean that the body resists histamine’s effects. Instead, histamine intolerance (HIT) means an impaired ability to break down histamine. Many researchers believe HIT starts in the gut with the deficiency of an enzyme, diamine oxidase, which breaks down histamine (3). Note that the term “lactose intolerance” is similar, meaning the impaired ability to break down lactose in the gut (4).
Contributors to Histamine Intolerance
Two enzymes can break down histamine for use by the body, diamine oxidase (DAO) and histamine N-methyltransferase (HNMT). If anything interferes with the normal functioning of these enzymes, it can negatively affect the breakdown of histamine. Unfortunately, many factors can disrupt the ability of these enzymes to break down histamine properly, leading to histamine intolerance (1, 2, 5).
1) Overconsumption of histamine in the diet – Many foods and alcoholic beverages contain histamine. Frequent ingestion of these items can lead to such a high volume of histamine that DAO and HMNT enzymes get overwhelmed, resulting in increasing amounts of intact histamine in the system, which causes adverse symptoms.
2) Medications – Certain medications inhibit DAO enzymes, keeping them from properly breaking down histamine. These medications include some antibiotics, analgesics, antihypertensives, and antihistamines (2).
3) Health conditions: Many inflammation-oriented disorders, such as chronic inflammation, allergies, and Mast Cell Activation Syndrome (MCAS), can produce so much histamine that it overwhelms the ability of DAO and HMNT enzymes to break it all down. Other health conditions can result in DAO enzyme deficiency, such as non-celiac gluten sensitivity (NCGS) and malabsorption of carbohydrates. Those with chronic fatigue syndrome (CFS) or myalgic encephalomyelitis (ME) are at greater risk of experiencing HIT.
4) Genetic factors: Mutations in DAO or HMNT genes can cause the creation of inactive or only partially active DAO and HMNT enzymes, significantly reducing the ability to break down histamine.
5) Naturally low levels of DAO or HMNT enzymes: There are individual differences in levels of enzymes in people due to differing chemistry and genetics. Some people will produce fewer DAO and HMNT enzymes because that is what is normal for their bodies. Unfortunately, this could lead to a buildup of histamine in those individuals.
Symptoms of Histamine Intolerance
Because histamine has many roles, a wide range of symptoms can occur when it builds up in the body. This expression in multiple body parts makes it extremely difficult to diagnose correctly, and sufferers can go for years with little relief due to misdiagnoses. According to one study which did careful tracking, gastrointestinal-related problems were the most commonly experienced symptoms of HIT. However, there was a long list of symptoms (see below). Close to 97% of HIT patients in that study indicated they had four or more symptoms. Bloating had the highest ranking in the severity category and had a prominent spot in the list of concurrent symptoms. The combination of bloating and postprandial fullness (fullness after a meal) took the top spot in that category. A shocking 45% of HIT sufferers had more than ten symptoms. Interestingly, it is common in women for HIT symptoms to disappear during pregnancy and return after birth. Below is the list of symptoms categorized by where the symptom is experienced in the body (4, 6).
abdominal pain and/or cramping
dysmenorrhea (painful cramps during menstruation)
intestinal colic (painful spasms in the intestines)
postprandial fullness (fullness after a meal)
swollen, reddened eyelids