One red, sticky eye that antibiotic drops do not clear: could it be canaliculitis?

One eye is red, sticky and irritated. You have used pharmacy drops, perhaps a second course from a clinic, and it settles a little and then comes back. If the redness sits near the inner corner of the eye, beside the nose, one condition is worth knowing by name: canaliculitis, an infection of the tiny drainage tube in the eyelid. It is uncommon, and a 2024 review says it is frequently misdiagnosed. This piece is about recognising it, not treating yourself.

When is a red, swollen inner corner urgent?

Go the same day if the inner corner of the eye is hot, swollen and painful, if there is fever, if the swelling spreads over the cheek or eyelid, or if your vision changes. That picture can be an infected tear sac, dacryocystitis, or a spreading infection of the tissues around the eye, and both need a doctor promptly.

Leeds Teaching Hospitals describe an acute tear sac infection as a red, painful swelling at the corner of the eye. The NHS lists a change in vision or severe eye pain as reasons to ask for urgent help with a watering eye. Canaliculitis is usually slower and more grumbling than this, but I would not want anyone to wait at home with a hot, painful swelling because the words "just canaliculitis" sounded gentle. I explain the sac infection in dacryocystitis: blocked tear duct infection.

What is canaliculitis, and what does it look like?

Canaliculitis is inflammation of the canaliculus, the fine channel inside the eyelid that carries tears from the eye towards the tear sac. A 2024 review in Seminars in Ophthalmology describes the classic picture as redness, mucopurulent discharge (sticky, pus-like mucus), swelling at the inner corner, a watering eye, and a pouting punctum.

Each of those needs a translation. The punctum is the tiny opening on the edge of each eyelid near the nose, where tears begin to drain. A "pouting" punctum means the opening looks slightly raised or turned out, as if it were pursing its lips, instead of lying flat. That is a sign an eye doctor checks with a slit lamp, the microscope used in the clinic, so you are not expected to spot it at home. What you may notice is one eye, one side, one corner: a red, swollen inner lid, sticky discharge that keeps returning, and tears that spill over the cheek.

The same review found that most patients were in their late fifties, on average 57 years, with more women than men, and that the lower canaliculus was involved more often than the upper. It analysed 100 published articles, so it describes what has been reported in the literature, and it does not tell you how likely any one person is to have it.

How is canaliculitis different from a blocked tear duct or a tear sac infection?

The difference is where the problem sits along the tear route. Tears leave through the punctum, run along the canaliculus, gather in the tear sac beside the nose, then pass down the nasolacrimal duct into the nose. Leeds and Cambridge University Hospitals describe this route. Canaliculitis is the start of the pipe. Dacryocystitis is the sac in the middle. A blocked nasolacrimal duct is the lower end.

That matters because they are treated differently. Dacryocystorhinostomy, or DCR, the operation that joins the tear sac to the nose, bypasses a blockage below the sac, according to Leeds, which is a different site from the canaliculus. The review's abstract mentions surgical management, and I would not want to summarise a surgical technique from an abstract. For the blocked duct itself see watery eyes and blocked tear ducts, and for an eyelid opening that is too narrow see punctal stenosis.

It helps to be clear about the scale. Canaliculitis is a localised infection of a very small structure, and a very small structure is hard to see without the right equipment. That is the practical reason an examination matters more than a third set of drops, and it is why I would want the corner of the eye looked at closely before anyone changes the treatment again.

Why is canaliculitis so often mistaken for conjunctivitis?

Because it looks like it. Conjunctivitis is inflammation of the thin clear layer over the white of the eye, and a red, sticky eye is the textbook picture of it. The 2024 review states that, despite having classical features, canaliculitis is frequently misdiagnosed, with many patients labelled as conjunctivitis or dacryocystitis. That is a statement about how easy the condition is to mistake, not about anyone's care.

The NHS says antibiotic drops can help if you have an eye infection, and for a true conjunctivitis that is sensible. The clue that something else is going on is the pattern: one eye only, the redness and discharge return soon after the drops finish, and there is fullness at the inner corner. As a general, unproven explanation, eye drops mostly bathe the surface of the eye, and an infection inside a fine tube in the lid may be harder for them to reach. That is a plain-language idea and not a finding from the review or any source used here, so please do not treat it as established. What the review does say is that management is difficult and recurrence is common.

If you have had two courses of drops for one red, sticky eye and it has come back, that is a good reason to be seen by an eye doctor before a third. Blepharitis, inflammation of the lid margin, can also look similar, and I cover it in sore, crusty eyelids. A punctal plug placed to treat dry eye can also be involved, because the review says the secondary form is mostly linked to plug use.

How is canaliculitis treated, and does it come back?

Treatment is decided by an eye doctor after examination, and surgery is common in the published reports. The review found surgery was used in 74.25 percent of the cases in the literature and medical treatment alone in 20.82 percent. It also says there are no universally accepted guidelines, that different medical and surgical options have been used with varying success, and that the condition is notorious for recurrence and failure of treatment.

Those figures come from articles gathered over 15 years, and published cases tend to favour those interesting enough to write up, so they are not a success rate and not a promise. The bacteria most often found were Staphylococcus, Streptococcus and Actinomyces. A 2026 review of fungal lacrimal infections found 118 reported cases in the literature, with Candida and Aspergillus the commonest, and only 14.4 percent of them involved the canaliculus alone. Fungal infection is uncommon, and I mention it only so you know the range of causes a doctor may think about.

Please do not squeeze the punctum, probe it, or try to express material from it at home, and do not restart old drops without advice. I would not give a step list here, because the right step depends on what the examination shows.

Who should I see, and what will they ask?

Start with an eye doctor. The NHS says a GP who cannot find the cause of watering eyes may refer you to an ophthalmologist for tests. An oculoplastic surgeon is an eye doctor trained in eyelids and tear ducts, and this is the kind of condition that falls in their area. Published Malaysian data on canaliculitis are limited, so I will not quote a local figure.

Expect questions about how long it has lasted, which eye, what you have tried, whether you have ever had a punctal plug, whether you have had eyelid or tear duct surgery, and whether anything lowers your immunity. Write the dates of each course of drops down before you go. For the wider tear system, see the hub for watery eyes and tear ducts, the guide to watery eyes in adults, and the general map, what makes eyes look tired.