Mast Cell Stabilizers / Antihistamines (Cromolyn, Ketotifen)

Also known as: cromolyn sodium (Gastrocrom), ketotifen (Zaditor/Zaditen), mast cell activation syndrome (MCAS) therapy

Other

In plain English

These medicines calm overactive mast cells (allergy cells). They are used for mast cell activation syndrome (MCAS) and related conditions to reduce flushing, hives, stomach/gut symptoms, and other allergic-type reactions. Cromolyn is especially helpful for gut symptoms; ketotifen is both an antihistamine and a mast cell stabilizer. They are generally well tolerated and used as part of a stepwise plan alongside standard antihistamines.

The science

Cromolyn sodium stabilizes mast cell membranes and reduces mediator release (histamine, tryptase) and is used, often poorly absorbed and locally acting in the gut, for GI symptoms of mast cell disease; ketotifen combines H1-antihistamine activity with mast cell-stabilizing properties. Expert frameworks for MCAS recommend baseline H1 and H2 antihistamines plus mast cell stabilizers as needed, though the supporting trials are generally small.

References

• Weiler CR et al., H1-antihistamines for primary mast cell activation syndromes (systematic review), Allergy 2015
• Valent P et al., mast cell activation syndromes: CIA update 2022, Int Arch Allergy Immunol 2022