An antihistamine (tablets and eye drops)
Ketotifen
An antihistamine with mast-cell-stabilising action, available as tablets for allergy and as eye drops for allergic conjunctivitis.
What is Ketotifen?
Ketotifen is an antihistamine that also stabilises mast cells, the cells that release allergy chemicals. As tablets it is used for allergic conditions but tends to cause drowsiness, while as eye drops it is used to relieve and prevent itchy, watery eyes from allergic conjunctivitis. The eye drops act locally and are far less likely to make you sleepy.
Education and reference only. This is a plain-language guide to Ketotifen — 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
Ketotifen comes in two quite different forms. The tablets are an antihistamine used for allergic conditions and, in some places, as add-on treatment in asthma — but they are sedating. The eye drops are widely used in the UK for allergic conjunctivitis (itchy, red, watery eyes from hay fever and other allergies), where they both relieve symptoms and help prevent them by calming the eye's allergic response.
How it works
Ketotifen blocks histamine H1 receptors and also stabilises mast cells, so they release fewer allergy-driving chemicals such as histamine. This dual action both relieves existing allergic symptoms and reduces flare-ups. In the eye drops the effect is mainly local, soothing the itch and redness of allergic conjunctivitis.
What it treats
Conditions Ketotifen is used for
Practical use
How to take Ketotifen
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- For the tablets, take them as prescribed, with food to reduce stomach upset; expect possible drowsiness.
- For the eye drops, wash your hands, tilt your head back and apply into the pocket of the lower lid, taking care not to touch the eye with the dropper.
- Use the eye drops regularly through the allergy season for the best preventive effect.
- Remove soft contact lenses before the drops and wait a short while before replacing them.
- With the tablets, avoid alcohol and do not drive until you know how they affect you.
- If you miss a dose, take it when you remember unless it is nearly time for the next — do not double up.
Weighing it up
Advantages & disadvantages of Ketotifen
Advantages
- The eye drops both relieve and help prevent allergic eye symptoms, and act locally with little drowsiness.
- Dual antihistamine and mast-cell-stabilising action gives sustained allergy control.
- Eye drops are convenient for hay-fever eye symptoms and suit regular seasonal use.
Disadvantages
- The tablets are sedating, so they can cause drowsiness and impair driving.
- Eye drops may sting briefly on application and the preventive benefit builds over days rather than instantly.
- Soft contact lenses must be removed for the drops, which is less convenient for lens wearers.
Practical use
Good to know
The tablets commonly cause drowsiness, so they suit times when you do not need to be fully alert; the eye drops act locally and rarely cause sleepiness. With the eye drops, the benefit builds with regular use, so they work best taken consistently through the allergy season rather than only when symptoms are bad. Remove soft contact lenses before using the drops and wait a short while before putting them back in.
Who should not take it / use with caution
- Avoid the eye drops if you are allergic to ketotifen or to ingredients such as the preservative in the drops.
- With the tablets, take care if you are very drowsy-prone, and check suitability in pregnancy or breastfeeding with a clinician.
- Soft contact lenses should not be worn while putting in the drops.
Monitoring
- Whether eye or allergy symptoms improve with regular use.
- Daytime drowsiness with the tablets.
- Any persistent eye irritation or worsening redness.
Side effects
- Eye drops: brief stinging or burning, mild eye irritation, dry eye or headache.
- Tablets: drowsiness, dry mouth and sometimes weight gain or dizziness.
- Rarely, increased sensitivity or an allergic reaction to the drops.
Key interactions
- With the tablets, alcohol and other sedating medicines add to drowsiness.
- If you use more than one type of eye drop, leave a short gap between them.
- Few important interactions with the eye drops, as little is absorbed into the body.
Available as: Eye drops, and tablets and an oral solution.
Answers
Ketotifen: frequently asked questions
Do ketotifen eye drops make you drowsy?
They are very unlikely to, because they act locally in the eye and little is absorbed into the body. The tablets, by contrast, commonly cause drowsiness.
How quickly do the eye drops work?
They start to ease itch fairly soon, but the full preventive benefit builds with regular use over a few days, so it is best to use them consistently through the allergy season.
Can I wear contact lenses with the drops?
Remove soft contact lenses before putting the drops in and wait a short while before replacing them, as the drops and their preservative can affect lenses.
What is the difference between the tablets and the eye drops?
The eye drops treat itchy, watery allergic eyes locally with little drowsiness. The tablets treat broader allergic symptoms but are sedating, so they are used differently.
Can I use the eye drops for hay fever?
Yes — they are commonly used for the itchy, red, watery eyes of hay fever and other allergic conjunctivitis, and work well when used regularly.
The wider class
About Antihistamines
Ketotifen belongs to the antihistamines class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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