"True" allergic reactions involve histamine, but histamine intolerance is different. Histamine intolerance refers to a reaction to foods that have high levels of naturally occurring histamine; in contrast, during a normal allergic reaction, the body itself produces high levels of histamine in response to a food it perceives as an invader. People with histamine intolerance often have low levels of either of two enzymes -- diamine oxidase (DAO) and histamine-N-methyltransferase (HNMT) -- that bind to and metabolize histamine. In these people, histamine can build up over time and cause symptoms throughout the body.
What Is Histamine:
Histamine is one of a group of nitrogen-containing compounds called amines. (Other common amines include amphetamines and pseudoephedrine.) Histamine is bioactive, which means that in the body, it has biological effects. It binds to special receptors in tissues throughout the body, thereby causing a variety of skin, gastrointestinal, nervous system and cardiac symptoms.
The most common symptoms of histamine intolerance are migraine headaches, gastrointestinal symptoms (such as diarrhea), flushing, hives, eczema, and allergic rhinitis. Histamine intolerance can also cause more severe symptoms. It can trigger asthma attacks or anaphylactic shock, can cause arrythmia, and may be associated with serious chronic conditions like Crohn's disease.
Most foods that are high in histamine are highly processed or fermented: wine, aged cheese, yeast-containing foods, and sauerkraut. Spinach and tomatoes are also high in histamine. In addition, while citrus fruits are not themselves considered high in histamine, they can release histamine in the body that is bound to mast cells. Therefore, people on a strict histamine-free diet are generally advised to avoid citrus.
Histamine and Alcohol:
"Red wine migraines" are often histamine intolerance headaches, and red wine is indeed high in histamine. But all alcoholic beverages can be problematic for people with histamine intolerance because alcohol can make DAO, one of the enzymes that metabolizes histamine in the body, less effective. Alcohol is therefore not allowed on a histamine-free diet.
- More about Alcohol Allergies and Intolerances.
Diagnosing Histamine Intolerance:
Recurring symptoms after eating high-histamine foods may lead doctors to suspect a histamine intolerance; a food log may be useful in this stage of diagnosis. Histamine intolerance differs from IgE-mediated food allergies in that concentrations of histamine in the body can build up over time. This can make diagnosing a histamine intolerance challenging, especially since traditional allergy tests like prick tests and RAST tests can't be used to diagnose non-IgE mediated allergies. Histamine intolerance can be diagnosed by a trial of a histamine-free diet followed by a double-blind food challenge.
Living With and Treating Histamine Intolerance:
Maintaining a strict histamine-free diet is the key to relief from histamine intolerance symptoms. Your doctor will discuss which foods you should avoid, but in general, fermented and aged foods and certain high-histamine vegetables are most likely to cause problems.
You should also let your doctor know about any medications, prescription or non-prescription, you're taking. Some medications can affect the action of DAO and HNMT. If you are on such a medication, your doctor may want to adjust your dosage, switch you to a similar medication that doesn't inhibit these enzymes, or, if possible, take you off the medicines entirely.
While a histamine-free diet is the only long-term treatment for histamine intolerance, there are a couple other treatments that may be useful. Benadryl (an antihistamine) may be useful in case you accidentally eat histamine-containing food or have to take a drug that can block DAO activity.
There are also supplements that some doctors recommend for people with histamine intolerance. They include high doses of vitamin C and vitamin B6 (which can stimulate the activity of DAO in the body) and capsules of DAO to supplement the body's natural supply. However, these treatments are, at this time, recommended for use alongside a histamine-free diet and not to allow people with histamine intolerance to eat foods containing histamine.
Maintz, Laura, et al.. "Evidence for a Reduced Histamine Degradation Capacity in a Subgroup of Patients with Atopic Eczema." Journal of Allergy and Clinical Immunology. May 2006, 117(5): 1106-12.
Maintz, Laura and Natalija Novak. "Histamine and Histamine Intolerance." American Journal of Clinical Nutrition. May 2007, 85(5): 1185-96. 8 June 2008.