Histamine plays an important role in healthy immune functioning and neurotransmitter signaling. However, when these naturally occurring substances don’t function appropriately, it can lead to problems. Dr. Bruce Hoffman offers explanations of what role histamine plays in a healthy immune response, and how histamine relates to mast cell activation syndrome, or MCAS, below.
What is histamine?
Histamine is a substance that naturally occurs in the body to help regulate bodily functions, including the immune response. It’s a signaling chemical or mediator, which means it helps send messages between various cells in your body, particularly of an immune nature. Mast cells in connective tissues are one of the areas where your body stores histamine along with many other mediators of inflammation. However, histamine is also present in certain foods, which means you can trigger histamine reactions due to the type of foods that you eat.
Histamine in healthy immune function
While histamine has numerous functions, Dr. Bruce Hoffman’s work with MCAS is mainly concerned with its role in healthy and unhealthy immune responses. In healthy immune function, your body releases histamine as a response to the presence of foreign proteins you are allergic to. Those histamines send messages to other areas of your body, causing symptoms of an allergic reaction to warn you of the presence of the allergy-related protein.
There are a few known histamine receptors in the body. The type of allergic reaction depends on which receptors histamine binds to when it is released. For example, when histamine binds to H1 receptors, symptoms can include itching skin, flushing, pain, narrowing airways that make it more difficult to breathe, expanding blood vessels, increased heart rate, and low blood pressure.
H2 receptors are located in your stomach, heart, and some muscle cells. When histamine binds to these receptors, the symptom response can include hypotension, flushing, change in heart rate, bronchoconstriction, and an increase in stomach acid.
What else does histamine do?
Histamine isn’t just a communication mechanism for allergic reactions. It also works in the body to help regulate food intake, emotions, learning and memory, body temperature, and sleeping and waking cycles. H3 histamine receptors are involved in the central nervous system and are believed to help regulate dopamine and other neurotransmitters. H4 receptors are involved in the formation of blood cells.
What is mast cell activation syndrome (MCAS) ?
MCAS occurs when you have an inappropriate overactive immune response that drives allergic or inflammatory responses, with or without an actual allergen being present. Histamine is one of the 1200 mediators of inflammation involved in MCAS because when it is released, it signals allergic responses. Foods with a high histamine content may increase symptoms or trigger a flare. That is because someone with MCAS is dealing with histamine dysregulation and imbalance already, so adding more histamine can make things worse.
Because histamine is dysregulated in someone with MCAS, the body can have a chronic, heightened immune response that leads to constant allergy-related symptoms, including:
- Pain
- Congestion
- Trouble with breathing or wheezing
- Hives or itching
- Flushing
- Stomach pain
- Constipation or diarrhea
- Heartburn or reflux
- Sneezing
- Changes in blood pressure
- Rapid heart rate
- Dizziness
- Fainting
- Trouble focusing
- Headaches
- Numbness in the hand, feet, arms, or legs
- Joint pain
- Muscle pain or weakness
- Swelling or bloating
These symptoms can vary in severity, ranging from mild and annoying to severe and life-threatening. Patients may experience flare-ups in response to external stimuli or internal changes related to stress or general health.
Histamine intolerance
Dr. Bruce Hoffman discusses the difference between histamine intolerance and MCAS. Histamine intolerance occurs when the body has a negative reaction when ingesting foods that include histamine. Foods and beverages that contain histamine include alcohol, some fermented foods, avocado, legumes, eggplant, some aged cheeses, certain kinds of dried fruit, wheat, mushrooms, spinach, highly processed foods, bananas, preserved olives, and many aged meats. This is not an exhaustive list, and a health care provider or dietician can help you understand what foods to avoid if you have a histamine intolerance or a condition that involves an exaggerated histamine response.
MCAS is different from histamine intolerance in that the body is not simply responding to histamines introduced via food. You may experience more severe symptoms when you eat these foods because you are adding to the problem that is already brewing with increased histamine levels in your body, although the outcome may be the same. People with MCAS may need to limit or avoid foods that are high in histamine.
The importance of histamine balance in health
Sometimes, antihistamine treatments can help suppress histamine responses and reduce the symptoms associated with MCAS. However, because histamine plays a role in so many bodily functions, you don’t want to suppress it completely. Dr. Bruce Hoffman addresses the need to balance histamine within the body for optimal functionality and health.