Cromolyn® Eye Drops: iDrop with Cromolyn®

What is seasonal ‘allergic conjunctivitis’?

It is basically fancy way to say your conjunctiva (layer of your eye that covers the white part) is inflamed due to an allergy! Many people experience swollen, itchy, or watery eyes during certain seasons of the year. These symptoms may be present with a runny, congested nose, or an itchy throat and palate1. If you have seasonal allergic conjunctivitis, your body’s immune system responds to allergy-causing agents such as pollen, ragweed, or dust and you experience these symptoms1!

How can you tell whether you have an eye infection, or eye allergies?

An eye infection is caused when a pathogen (a bacteria, virus, or other microorganism capable of causing an infection) enters the eye and causes inflammation1. This can result in a milky coloured discharge, redness, pain, burning, and itching2. These symptoms are usually present in one eye, or start in one eye and end up in both2. If you think you may have an eye infection, contact your pharmacist or doctor immediately. Usually eye infections are treated with an antibiotic to help eliminate the pathogen and stop those irritating symptoms 2.

An allergic reaction in the eye is when a foreign particle or substance enters your eye and causes your immune system to overreact3. These particles may not cause a reaction in everyone, but for some people who have a more sensitive immune system this results in both eyes feeling itchy, watery, and inflamed1,3. These types of reactions can often be treated with over the counter solutions, such as Cromolyn® eye drops; however, if you are experiencing very severe symptoms, contact your health care professional.

What are Cromolyn® eye drops?

Cromolyn® eye drops are an over-the-counter option for those suffering from seasonal allergic conjunctivitis. The active ingredient is sodium cromoglycate 2%. These eye drops are considered to be anti-allergic and are suggested for use in seasonal allergic conjunctivitis4.

How do this eye drop work?

The symptoms that you experience with seasonal allergic conjunctivitis are due to mast cell degranulation5. Woah, sounds like a mouthful; basically, when your eyes come into contact with an allergen, these cells called ‘mast cells’(cells involved in allergic responses), release a chemical called histamine. Histamine is responsible for inflammation, itchiness, red, and watery eyes3.

Sodium cromoglycate 2% (the main active ingredient in the eye drops) stabilizes these ‘mast cells’5,6. This helps stop the release of histamine from mast cells; therefore, stopping inflammation and providing comfort to the eyes5.

What does the evidence say?

Numerous studies have been conducted on the efficacy of Cromolyn® eye drops in comparison to other eye drop treatments and placebos. Most of the studies have concluded that using eye drop treatments, such as Cromolyn® (sodium cromoglycate), Alomide® (lodoxamide) and Alocril® (nedocromil sodium), are found to manage allergy symptoms better than using nothing. However, there are no significant differences between these particular eye drops 8, 9.

Comparisons were also done on drops that had preservatives and some without preservatives. These studies showed no difference in efficacy10. Both types of drops showed improvement of allergic conjunctivitis symptoms and the formulations were equally stable10.

Cromolyn® eye drops should be used regularly: 1-2 drops four times daily. One study compared Cromolyn® eye drops used regularly with an ‘as needed’ regimen. Those who used the drops ‘as needed’ (after the eye symptoms started) required other allergy treatments on top of the eye drops to relieve their symptoms11. The eye drops work better with regular dosing before allergy symptoms fully set in5, 11.

Are there any safety concerns?

Cromolyn® eye drops are generally safe although some stinging of the eye has been reported3.  The less frequent side effects include dryness around the eyes, puffy eyes, and eye irritation; however, these side effects have not been proven to be reactions to the drug3. This drug should not be used if there is an eye injury or infection. Contact lenses should not be worn when using this product3. There are no dangers when using these drops during pregnancy or lactation3.

Avoid Cromolyn® eye drops if there are allergies to any of the ingredients. No studies have been conducted on the safety of this product for children 5 years of age and under3.

The Bottom Line

The use of Cromolyn® eye drops in people with seasonal allergic conjunctivitis (eye allergies) is promising. It is very important that this product is used four times daily on a regular basis, which can sometimes be difficult! To get the best results, these drops should be started before you feel any symptoms (right before you think your eye allergies will kick in). If you are willing to ‘iDrop’ four times daily, and start treatment before allergy symptoms arise, Cromolyn® should do a good job in minimizing your eye allergy symptoms and provide relief!





Nisreen Chehimi, Hiba Halabi, Diva Niaz, and Jasjot Nijjar
BSc. Pharm Candidate(s)

Faculty of Pharmacy and Pharmaceutical Sciences

University of Alberta

Edited and Reviewed by the Health Aisle Team 



  1. Friesen, Anne M. (2014). Eye Care: Conjunctivitis. Therapeutic choices for Minor Ailments. Retrieved from:
  2. Mangat, R. (2014). The Diagnosis & Management of Ocular Disease – A Brief Overview. Personal Collection of R. Mangat, University of Alberta, Edmonton AB.
  3. (2013). Cromolyn® Eye Drops. E-Therapeutics+/e-CPS/Therapeutic Choices. Retrieved from:
  4. Pendopharm. (2013). Cromolyn® Eye Drops: Product Monograph. Montreal, QC: Pendopharm, Division of Pharmascience Inc.
  5. Doughty, M.J. (1996). Sodium cromoglycate ophthalmic solution as a Pharmacy Medicine for the management of mild-to-moderate, non-infectious inflammation of the conjunctive in adults. Ophthalmic and Physiological Optics, 6(2): S33-S38.
  6. Suonpaa, J. (1996). Treatment of Allergic Rhinitis. Annals of Medicine, 28: 17-22.
  7.  Leino, M., Montan, P., & Nja, F. (1994). A double-blind group comparative study of ophthalmic sodium cromoglycate, 2% four times daily and 4% twice daily, in the treatment of seasonal allergic conjunctivitis. Allergy, 49: 147-151.
  8. James, I., Campbell, L., Harrison, J., Fell, P., Ellers-Lenz, B., & Petzold, U. (2003). Comparison of the efficacy and tolerability of topically administered azelastine, sodium cromoglycate and placebo in the treatment of seasonal allergic conjunctivitis and rhino-conjunctivitis. Current Medical Research and Opinion, 19(4), 313-320.
  9.  Leion, M., Ennevaara, K., Latvala, A.L., Nordgren, P., Posti, A.M., Suves, R., & Takalo, E. (1992). Double-blind group comparative study of 2% nedocromil sodium eye drops with 2% sodium cromoglycate and placebo eye drops in the treatment of seasonal allergic conjunctivitis. Clinical and Experimental Allergy, 22: 929-932.
  10. Yi-Hao, C., Ching-Long, C., Jian-Nan, W., & Da-Wen, L. (2007). Efficacy and Safety of Cromolyn® Sodium Ophthalmic Solution with and without Preservative in Allergic Conjunctivitis. Journal of Medical Sciences, (2), 67.
  11. Juniper, E.F., Guyatt, G.H., Ferrie, P.J., & King, D.R. (1994). Sodium cromoglycate eye drops: Regular versus “as needed” use in the treatment of seasonal allergic conjunctivitis. Journal of Allergy and Clinical Immunology, 94(1): 36-43.