Mast cell stabilizers are a group of medications that prevent the release of inflammatory substances from a specific type of immune cell. This action helps to manage and reduce the symptoms associated with various allergic and inflammatory conditions. By intervening before an allergic reaction begins, these medications serve a preventative role, focusing on the initial stages of an allergic cascade to stop symptoms before they start.
The Role of Mast Cells in the Body
Mast cells are a type of immune cell found in connective tissues throughout the body, particularly near blood vessels, nerves, and in the lungs and intestines. These cells are sentinels, ready to act against foreign invaders or allergens. They contain hundreds of tiny sacs, or granules, filled with chemicals known as mediators.
When a mast cell encounters a substance it identifies as a threat, such as pollen or pet dander, it becomes activated. This activation triggers a process called degranulation, where the mast cell releases the contents of its granules into the surrounding tissues. These mediators include histamine, leukotrienes, and prostaglandins.
The release of these chemicals initiates an inflammatory response. Histamine, for example, increases blood flow, causes blood vessels to become more permeable, and contributes to the classic symptoms of an allergic reaction, such as swelling, itching, and mucus production. Leukotrienes are involved in sustaining inflammation and can cause the tightening of airway muscles, a prominent feature in asthma.
Mechanism of Action
Mast cell stabilizers prevent the release of inflammatory mediators by reinforcing the outer membrane of the mast cell, making it less likely to release its contents when it comes into contact with an allergen. This stabilization is accomplished by controlling specific channels in the cell’s membrane.
The process of degranulation is dependent on an influx of calcium ions into the mast cell. When an allergen binds to IgE antibodies on the surface of a mast cell, it signals calcium channels to open, allowing calcium to rush into the cell. This influx of calcium is the direct trigger for the granules to fuse with the cell membrane and release their chemical mediators.
Mast cell stabilizers block these IgE-regulated calcium channels. By preventing or significantly reducing the amount of calcium that can enter the cell, the medication interrupts the signaling cascade that leads to degranulation. Without a sufficient concentration of intracellular calcium, the granules cannot merge with the cell membrane to release their contents.
Medical Applications and Conditions Treated
Mast cell stabilizers are used to manage a variety of conditions driven by mast cell activation. One of their most common applications is in the treatment of allergic rhinitis (hay fever), where they help prevent symptoms like sneezing, congestion, and a runny nose. They are also frequently used for allergic conjunctivitis, an inflammation of the eye’s membrane, to reduce itching, redness, and watery eyes.
For individuals with certain types of asthma, particularly those with mild to moderate disease, mast cell stabilizers can be used to prevent the airway constriction caused by exposure to allergens. They are used to maintain clear airways rather than to treat an active asthma attack.
A less common use is managing mastocytosis and Mast Cell Activation Syndrome (MCAS). These conditions are characterized by an excessive number of mast cells or overly reactive mast cells. In these cases, oral forms of mast cell stabilizers can help reduce widespread and chronic symptoms.
Types of Mast Cell Stabilizers
Mast cell stabilizers are available in various formulations, many requiring a prescription. Cromolyn sodium is a well-known prescription stabilizer administered through an inhaler for asthma, a nasal spray for allergic rhinitis, or in an oral form for mastocytosis. Other prescription options include ketotifen, nedocromil, and lodoxamide.
Over-the-counter (OTC) options are also available for targeted relief. The most common OTC mast cell stabilizer is cromolyn sodium, sold as a nasal spray under brand names like NasalCrom. Eye drops containing stabilizers like ketotifen, lodoxamide, and pemirolast are also available to treat allergic conjunctivitis.
Beyond pharmaceuticals, some natural compounds have been studied for their potential mast cell-stabilizing effects. Quercetin, a flavonoid present in foods like onions, apples, and berries, and luteolin, found in celery and green peppers, are two such compounds. Research is ongoing and the results are not yet conclusive.
Distinguishing from Other Allergy Medications
The primary difference between mast cell stabilizers and other allergy treatments, like antihistamines, is their timing and mechanism. Mast cell stabilizers are prophylactic, meaning they must be used consistently before allergen exposure to be effective. They work by preventing the initial release of histamine.
Antihistamines, in contrast, are for symptomatic relief. They work by blocking histamine from binding to its receptors after it has been released from the mast cells. This action reduces symptoms like itching and swelling but does not prevent the degranulation process.
The two classes of medication are suitable for different purposes. A person with seasonal allergies might use a mast cell stabilizer daily to prevent symptoms and an antihistamine for immediate relief if symptoms break through. Some medications, known as dual-activity agents like olopatadine and ketotifen, combine both actions by stabilizing mast cells and blocking histamine receptors.