Mast cells are a component of the immune system whose overactivity can lead to symptoms of allergies and inflammation. While part of the body’s defense mechanisms, their oversensitivity can contribute to various health issues.
Understanding Mast Cell Activation
Mast cells are part of the immune and neuroimmune systems, located in connective tissues where the body interfaces with the external environment, such as the skin, gastrointestinal tract, and respiratory system. These cells act as a microscopic alarm system, housing granules filled with powerful chemical mediators.
When a mast cell encounters a trigger like an allergen, it initiates a process called degranulation. This involves the rapid release of its granular contents, including histamine and leukotrienes, into the surrounding tissue. This release drives the classic symptoms of an allergic reaction, such as swelling, itching, and inflammation.
For an allergic reaction, an antibody known as immunoglobulin E (IgE) on the mast cell’s surface must bind to the allergen. The cross-linking of two or more of these IgE molecules is required to trigger the mast cell to degranulate. Other stimuli, including certain medications, physical injury, or microbial pathogens, can also activate mast cells.
The Mechanism of Mast Cell Stabilization
Mast cell stabilizers work by interrupting the activation process before it can lead to symptoms. Their primary function is to reinforce the mast cell membrane, making it less likely to rupture and release its contents when it encounters a trigger. This mechanism is preventative, aiming to stop the inflammatory cascade before it begins.
The core action of most mast cell stabilizers involves blocking specific channels that allow calcium to enter the cell. The influx of intracellular calcium is a necessary step for the granules to fuse with the cell membrane and degranulate. By preventing this calcium influx, stabilizers keep the mast cell in a stable, inactive state.
This preventative action distinguishes mast cell stabilizers from antihistamines. While stabilizers prevent the release of histamine, antihistamines work after the fact. Antihistamines operate by blocking the histamine receptors on other cells, preventing effects like itching and swelling.
Pharmaceutical Mast Cell Stabilizers
Several pharmaceutical mast cell stabilizers are available in various forms to target specific areas. One of the most established is Cromolyn sodium. It is available as a nasal spray (Nasalcrom) for allergic rhinitis, eye drops (Opticrom, Crolom) for allergic conjunctivitis, and an oral solution (Gastrocrom) for mastocytosis. An inhaler version is also used for asthma.
Another widely used medication is Ketotifen, which possesses the dual action of being both a mast cell stabilizer and an H1-antihistamine. In the United States, Ketotifen is available over-the-counter as eye drops (Zaditor), but oral formulations for conditions like Mast Cell Activation Syndrome (MCAS) must be prepared by a compounding pharmacy.
Other prescription stabilizers include lodoxamide and pemirolast, which are also formulated as eye drops for allergic conjunctivitis. These medications are designed to act locally, minimizing systemic absorption. The choice of stabilizer and its formulation depends on the specific condition being treated.
Natural Compounds with Stabilizing Effects
Beyond pharmaceuticals, several natural compounds found in foods and supplements have demonstrated mast cell-stabilizing properties. The flavonoids quercetin and luteolin are among the most studied for these effects. These plant-based compounds are believed to inhibit the release of histamine and other inflammatory mediators from mast cells, functioning in a way that complements dietary strategies for managing allergic symptoms.
Quercetin is abundant in a variety of common foods. Rich sources include:
- Onions
- Capers
- Apples
- Broccoli
- Black tea
Luteolin can be found in foods like chamomile, carrots, and celery. While these compounds are available in supplement form, obtaining them through whole foods contributes to a broader intake of nutrients.
Vitamin C is another nutrient that supports mast cell stability. Research has indicated that as blood levels of vitamin C decrease, histamine levels can increase, suggesting a regulatory role. While many fruits and vegetables are high in vitamin C, individuals on low-histamine diets may need to select sources like bell peppers or broccoli over citrus fruits.
Safety and Considerations for Use
Mast cell stabilizers are generally considered safe, with the most common side effects being minor and localized, such as brief irritation from nasal sprays or eye drops. When taken orally, some individuals may experience gastrointestinal discomfort or headaches. Serious side effects are uncommon, and these medications have a long history of use.
A primary consideration is that these medications are prophylactic, meaning they work to prevent symptoms rather than relieve them acutely. It may take several weeks of consistent, regular use for the full protective effects to be realized. This is because they do not counteract mediators that have already been released into the tissues.
Before beginning any new medication or supplement regimen, consultation with a healthcare professional is important. This is particularly true for individuals with underlying health conditions, such as kidney or liver disease, as dosages may need adjustment. It is also important for those who are pregnant or breastfeeding to seek medical advice before use.