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Understanding Allergy and Hay Fever Medications (cont.)

Mast Cell Inhibitors

Cromolyn sodium (Nasalcrom, Crolom) is used to prevent allergic symptoms like runny nose or itchy eyes. Cromolyn sodium must be started one to two weeks before pollen season and continued daily to prevent seasonal allergy symptoms. The response is not as strong as that of corticosteroid nasal sprays.

  • How mast cell inhibitors work: These drugs prevent the release of histamine and other chemicals that cause allergic symptoms from mast cells when an individual comes into contact with an allergen like pollen.
  • Who should not use these medications: Individuals who are allergic to any components of the nasal spray or eyedrops should not take mast-cell inhibitors.
  • Use: Frequent dosing is necessary, since the effect only lasts up to eight hours. Mast-cell inhibitors are available as nasal sprays to prevent runny nose or eyedrops for itchy eyes.
  • Drug or food interactions: Since these drugs have little or no effect beyond the area applied, they are unlikely to interact with other drugs.
  • Side effects: Contact lenses should not be worn if using eyedrops. Eyedrops may cause stinging, burning, redness, and, possibly, severe swelling of eyes. Nasal congestion, sneezing, itching, nosebleeds, and burning have been reported with use of cromolyn sodium nasal sprays.

Medically reviewed by Michael Manning, MD; American Board of Allergy & Immunology


Sheikh, Javed, and Umer Najib. "Allergic Rhinitis." eMedicine. June 16, 2009. <>.

Weiner, J.M., M.J. Abramson, and R.M. Puy. "Intranasal Corticosteroids Versus Oral H1 Receptor Antagonists in Allergic Rhinitis: Systematic Review of Randomised Controlled Trials." BMJ 317.7173 Dec. 12, 1998: 1624-9.

Medically Reviewed by a Doctor on 5/17/2016

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