[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Ophthalmic antiallergics

# Ophthalmic antiallergics

Eye drops for itchy allergic eyes: antihistamines that also steady mast cells (olopatadine, ketotifen) and pure mast cell stabilisers.

Updated Nov 1, 2026

## What they are

Topical drugs for allergic conjunctivitis caused by pollen, dust, animal dander and similar allergens. Dual-action drops block H1 receptors for fast relief of itching and also reduce mast cell release, which helps prevent new symptoms.

## Mechanism of action

In allergic conjunctivitis allergen binds IgE on conjunctival mast cells, which release histamine and other mediators. Histamine on H1 receptors causes itching, redness and swelling. Olopatadine and ketotifen block H1 receptors and stabilise mast cells; cromoglicate-type drugs only stabilise mast cells and work best when started before exposure.

Target: Histamine H1 receptors and conjunctival mast cells

## Key points

- Itching is the hallmark of allergic conjunctivitis; these drops target it.
- Not for contact-lens irritation; lenses come out before the drop and stay out if the eye is red.
- Benzalkonium chloride in many drops is absorbed by soft lenses.
- Eye pain, vision change or worsening redness needs review: it may not be allergy.

## Drugs in this class

- [**Olopatadine** An antihistamine eye drop that also steadies mast cells. It relieves the itch of allergic conjunctivitis caused by… Histamine H1 receptor (plus mast cell stabilisation)](https://durgical.com/en/pharmacology/olopatadine/)
- [**Ketotifen** An antihistamine eye drop that also steadies mast cells. It relieves the itch of allergic conjunctivitis for several… Histamine H1 receptor (plus mast cell stabilisation)](https://durgical.com/en/pharmacology/ketotifen/)

## Others in the class

- Azelastine, epinastine, alcaftadine, bepotastine (antihistamine drops)
- Sodium cromoglicate, lodoxamide, nedocromil (mast cell stabilisers)

## Test yourself

Think of the answer, then tap the question to see it.

## Which symptom is the hallmark of allergic conjunctivitis?

Itching.

## What two actions do olopatadine and ketotifen share?

H1 receptor blockade and mast cell stabilisation.

## Why are pure mast cell stabilisers started before the allergy season?

They prevent mediator release but do not block histamine that is already released.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Olopatadine Ophthalmic: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a602025.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [Ketotifen Ophthalmic: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a604033.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=S01GX) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/classes/ophthalmic-antiallergics/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/ophthalmic-antiallergics/