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Cromolyn

Brand names: NasalCrom, Gastrocrom, Crolom (eye)

Cromolyn prevents allergy symptoms by calming the cells that release histamine. It comes as a nasal spray, eye drops, and an oral liquid.

Brand namesNasalCrom, Gastrocrom, Crolom (eye)
Type of medicineMast cell stabilizer
Prescription?Over the counter (nasal); prescription (others)
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It works best started before allergy exposure and used regularly.

What it's used for

  • Preventing nasal allergy symptoms
  • Itchy allergy eyes
  • Mastocytosis (oral)

How to take it

  • Nasal: one spray in each nostril 3 to 4 times a day.
  • It may take 1 to 2 weeks for full effect.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Nose irritation
  • Sneezing
  • Bad taste
Call 911Swelling of the face, lips, or throat, hives, or trouble breathing

Warnings

  • It doesn't relieve symptoms that have already started.

Other medicines, foods, and alcohol

  • Few interactions.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Generally considered safe. Ask your provider.

Missed doses, overdose, and storage

If you miss a dose

This medicine is often taken only when needed. If you take it on a schedule, take a missed dose when you remember, unless it's almost time for the next one. Don't double up.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.