Sodium cromoglicate eye drops (mast-cell stabiliser)
Sodium cromoglicate
A preventer eye drop for allergy that works best used regularly to stop itchy, watery eyes.
What is Sodium cromoglicate?
Sodium cromoglicate is a mast-cell stabiliser eye drop used for allergic conjunctivitis, such as hay-fever eyes. Rather than treating symptoms once they appear, it calms the allergy cells so they release less of the chemicals that cause itching and watering. Because it works as a preventer, it is most effective when used regularly, usually several times a day, and can take a few days to build up its full effect. It is available from pharmacies and soft contact lenses should be removed before using it.
Education and reference only. This is a plain-language guide to Sodium cromoglicate — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Sodium cromoglicate is an eye drop used to prevent and relieve allergic conjunctivitis, including hay-fever-related itchy, red and watery eyes. It belongs to a group of medicines called mast-cell stabilisers. Mast cells are the allergy cells that release histamine and other chemicals when the eye meets a trigger such as pollen. Sodium cromoglicate steadies these cells so they release less of those chemicals. It is available to buy from pharmacies and is also prescribed within the UK health service.
How it works
Sodium cromoglicate works on the mast cells in the surface of the eye, making them more stable so that contact with an allergy trigger sets off a smaller reaction. With less histamine and fewer other chemicals released, there is less itching, redness, swelling and watering. Because it acts mainly to prevent the reaction rather than to switch off symptoms already present, it works best when used regularly before and during the allergy season. Its full benefit builds up over a few days of consistent use.
Company & origin
Originated / developed by: Sanofi (originator).
A long-established UK allergy eye drop, available from pharmacies, used regularly to prevent allergic eye symptoms.
Practical use
How to take Sodium cromoglicate
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Wash your hands, tilt your head back, pull down the lower lid and let one drop fall into the pocket without touching the eye.
- Use it regularly several times a day, even when your eyes feel comfortable, to keep it working as a preventer.
- Keep using it through the allergy season rather than only when symptoms flare, as the benefit builds up over a few days.
- Remove soft contact lenses before using the drops and wait a short while before putting them back in.
- Close the eye gently after the drop and press the inner corner briefly, and never share your drops with anyone.
Weighing it up
Advantages & disadvantages of Sodium cromoglicate
Advantages
- Helps prevent allergic eye symptoms when used regularly through the season.
- Available from pharmacies without needing a prescription.
- Acts on the eye surface, so effects on the rest of the body are limited.
Disadvantages
- Works best as a regular preventer, so it needs frequent, consistent use.
- Can take a few days to reach its full effect, so it is not a fast reliever.
- Soft contact lenses must be removed before each dose.
Practical use
Good to know
Sodium cromoglicate is a preventer, so it works best when used regularly, usually several times a day, even on days when the eyes feel well, and it can take a few days to reach its full effect. During the hay-fever season many people start it before symptoms peak and keep using it throughout. Remove soft contact lenses before using it and wait before putting them back in, as preservative in some versions can be absorbed by the lens. It can sting briefly and blur vision for a moment after application. Wash your hands first and avoid touching the eye or lashes with the dropper tip; if the eye becomes painful, very red or light-sensitive, get it checked.
Who should not take it / use with caution
- Anyone who has had an allergic reaction to sodium cromoglicate or other ingredients in the drops.
- People with a painful, very red eye or light sensitivity should be assessed rather than self-treating.
- Soft contact lens wearers should not use preserved drops with lenses in.
Monitoring
- Review if symptoms do not improve after using it regularly for several days.
- Seek advice if the eye becomes painful, very red or light-sensitive.
- Check that symptoms are due to allergy rather than infection.
Side effects
- Brief stinging or burning when the drop goes in.
- Temporary blurred vision just after application.
- Mild irritation or redness of the eye.
Key interactions
- Leave a gap between this and any other eye drops so neither is washed out.
- Soft contact lenses can absorb preserved drops, so remove lenses first.
- No important interactions with medicines taken by mouth are expected.
Available as: Eye drops in multidose bottles and preservative-free single-use units.
Answers
Sodium cromoglicate: frequently asked questions
Why does it take a while to work?
It is a preventer that steadies the allergy cells, so its effect builds up over a few days of regular use rather than acting instantly.
Should I keep using it if my eyes feel fine?
Yes, during the allergy season use it regularly even on good days, as it works by preventing reactions rather than just treating them.
Can I wear contact lenses with it?
Remove soft lenses before each dose and wait before putting them back, as the lens can absorb preserved drops.
Do I need a prescription?
No, sodium cromoglicate eye drops can be bought from pharmacies and are also available within the UK health service.
When should I see someone instead?
If the eye is painful, very red or sensitive to light, or your vision changes, get it checked rather than relying on allergy drops.
The wider class
About Allergy eye drops (mast-cell stabiliser)
Sodium cromoglicate belongs to the allergy eye drops (mast-cell stabiliser) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.