What Is Cromolyn?

Cromolyn Sodium (brand name Gastrocrom) is a mast cell stabilizer used to treat systemic mastocytosis, mast cell activation syndrome (MCAS), and allergic conditions. It works by preventing mast cells from releasing inflammatory chemicals like histamine and leukotrienes. The oral solution is primarily prescribed for mastocytosis symptoms including diarrhea, flushing, headaches, abdominal pain, nausea, and itching. The nasal spray form (NasalCrom) is available over the counter for allergic rhinitis, and an ophthalmic solution treats allergic conjunctivitis.

How does Cromolyn work?

Cromolyn Sodium stabilizes mast cells by preventing degranulation — the process where mast cells release inflammatory mediators like histamine and leukotrienes. Unlike antihistamines, which block histamine after it has already been released, Cromolyn prevents the release from happening in the first place. This makes it a preventive medication that must be taken consistently (typically 2–6 weeks) before full therapeutic benefit is seen. It has very low systemic absorption (0.5–2% bioavailability), meaning it acts primarily locally in the GI tract, nasal passages, or airways depending on the formulation.

What doses are available for Cromolyn?

• Oral solution (concentrate): 100 mg/5 mL ampules — the most commonly prescribed form for mastocytosis and MCAS
• Nasal spray (NasalCrom): 5.2 mg per actuation — available OTC for allergic rhinitis
• Ophthalmic solution: 4% — prescription for allergic conjunctivitis
• Nebulization solution: 20 mg/2 mL — largely unavailable
• Compounded oral capsules: 100 mg or 200 mg — available from compounding pharmacies when the oral solution is out of stock

How hard is it to find Cromolyn in stock?

Cromolyn Sodium oral solution has a findability score of just 30 out of 100, meaning it is very difficult to locate in stock at most pharmacies. An active FDA shortage that began in mid-2023 continues into 2026, driven by API sourcing difficulties, manufacturer exits (Woodward discontinued production), and NDC number changes causing pharmacy ordering confusion. Patients across 43+ states have reported being unable to fill their prescriptions. The nasal spray (NasalCrom) is more readily available OTC, but the oral solution remains scarce.

Who Can Prescribe Cromolyn?

Cromolyn Sodium oral solution is most commonly prescribed by allergists/immunologists and gastroenterologists, particularly for patients with mastocytosis or MCAS. Hematologists and oncologists may prescribe it for systemic mastocytosis, while pulmonologists historically prescribed the inhaled form for asthma (now largely discontinued). Primary care physicians and internists can also prescribe Cromolyn. The nasal spray (NasalCrom) is available OTC and does not require a prescription. Telehealth consultations are available for obtaining prescriptions.

Is Cromolyn a controlled substance?

No, Cromolyn Sodium is not a controlled substance and has no DEA scheduling. It has no potential for abuse or dependence. The oral solution requires a prescription, but the nasal spray (NasalCrom) is available over the counter without a prescription.

Common Side Effects of Cromolyn

• Headache
• Diarrhea
• Nausea
• Muscle aches (myalgia)
• Itchiness
• Abdominal pain
• Unpleasant taste
• Skin rash

Serious but rare side effects include severe allergic reaction (anaphylaxis), worsening of symptoms, joint pain and swelling, and difficulty swallowing. Contact your doctor immediately if you experience any serious side effects.

Alternative Medications to Cromolyn

• Ketotifen: A mast cell stabilizer and antihistamine commonly used as an alternative for MCAS and mastocytosis. Available as compounded oral capsules or OTC eye drops (Zaditor).
• Nedocromil (Tilade/Alocril): Another mast cell stabilizer with a similar mechanism to Cromolyn, though oral availability is limited.
• Hydroxyzine: An H1 antihistamine that helps control histamine-related symptoms like itching and flushing, though it does not stabilize mast cells.
• Famotidine (Pepcid): An H2 antihistamine often used alongside other therapies to manage GI symptoms in mast cell disorders. Widely available OTC.

Drug Interactions with Cromolyn

• Cromolyn Sodium has no significant known drug-drug interactions due to its very low systemic absorption (0.5–2% bioavailability) and the fact that it is not metabolized by cytochrome P450 enzymes.
• Food interactions: The oral solution should be taken 30 minutes before meals on an empty stomach. Do not mix with fruit juice, milk, or food, as this can reduce effectiveness.
• Always inform your doctor about all medications and supplements you are taking, even though Cromolyn interactions are unlikely.

Final Thoughts on Cromolyn

Cromolyn Sodium remains an essential medication for patients with mastocytosis and MCAS, but the ongoing shortage that began in 2023 continues to make it very difficult to find in 2026. With a findability score of just 30/100, patients should plan ahead, check multiple pharmacies, and consider alternatives like compounded versions or substitutes such as Ketotifen when Cromolyn is unavailable. Using tools like Medfinder can help locate pharmacies that currently have Cromolyn in stock without the frustration of calling around. If you are struggling to afford Cromolyn, patient assistance programs like Prescription Hope ($70/month) and discount cards from GoodRx can significantly reduce costs.