Mast cell stabilizers are a class of medication used to prevent or treat inflammation in individuals with allergies and some types of asthma. These medications generally have fewer and milder side effects than antihistamines, but they also take longer to work and are not as effective in relieving symptoms.

Mast cell stabilizers are usually taken continuously over a period of time to lessen the severity of allergy or asthma reactions. Like antihistamines, mast cell stabilizers work by interrupting the allergic cascade to prevent or reduce symptoms.

Mast cells are a type of white blood cell that plays a key role in allergic reactions. When an allergen enters the body and is encountered by the immune system, the allergen stimulates the release of antibodies that attach themselves to mast cells. On any subsequent contact with the allergen, the antibodies will trigger the mast cells to release histamine and other chemicals which are directly responsible for causing symptoms (e.g., swelling, itching, runny nose).

Mast cell stabilizers work by stopping mast cells from degranulating (releasing their chemicals). By interfering with this critical stage of the allergic cascade, the medication prevents the release of the inflammatory chemical histamine and other mediators of allergy and asthma. Mast cell stabilizers are only effective if they are already present in the body when an allergic reaction is triggered. 

Mast cell stabilizers usually last four to eight hours and cannot effectively treat symptoms unless they have been taken regularly for two to four weeks. While antihistamines and corticosteroids are both successful at treating early phase allergic reactions (occurring within minutes of exposure to the allergen), neither are considered effective at treating late phase reactions (occurring three to 12 hours after exposure). Mast cell stabilizers are effective at preventing late phase reactions.

Asthma attacks that occur as a result of an allergic reaction can be successfully treated with mast cell stabilizers. Although mast cell stabilizers are effective at managing mild persistent asthma, moderate or severe persistent asthma is more effectively managed with mid to high-dose inhaled corticosteroids.

Mast cell stabilizers are most frequently used by individuals who need to limit their exposure to side effects. This may include children, the elderly or individuals with medical conditions that can be complicated by side effects.