Can an Antibiotic Cause Dry Eye? What 2,243 Australian Dogs Showed
A sulfonamide antibiotic is known to cause dry eye in some dogs. In Australian records, definite cases were rare, about 1 in 500. What to watch for.
Written by thecanineledger
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If your dog develops a thick, sticky eye discharge, red eyes, squinting or a dull-looking eye during or after a course of medicine, call your vet the same day. Don’t stop the medicine without asking.
Our note: This advice is ours, not the paper’s. If you’re unsure, call your vet.
A widely used antibiotic combination from the sulfonamide family has been linked to dry eye, or keratoconjunctivitis sicca (KCS), in dogs. Dry eye means the eye doesn’t make enough tears. In Australian vet records, 2,243 dogs were treated with it, and only 4 had a definite diagnosis of dry eye afterwards (Hardefeldt et al., Journal of Veterinary Internal Medicine 2026). The authors conclude that dry eye “is rare in dogs treated with” the drug.
While that is reassuring, another 35 dogs had possible dry eye. Counting those, the figure rises to 1.8%.
→ Dry Eye (KCS): Why Treatment Is Usually Lifelong
1. The study
The dogs. Researchers used VetCompass Australia, a database of primary-care vet records, from 2012 to 2022. They used computer models that read clinical notes to find dogs given the antibiotic and dogs that later had signs of dry eye. They then checked the possible cases by hand.
Definite or possible. A case was definite if a tear test showed very low tear production along with typical signs. Other suggestive cases were counted as possible.
Funding. An Australian Research Council award funded the work. The authors declare no conflicts of interest.
2. What it found
| Measure | Result |
|---|---|
| Dogs treated | 2,243 |
| Definite dry eye | 4 (0.19%) |
| Definite or possible dry eye | 39 (1.8%) |
Dose and length of treatment. Neither was linked to dry eye in this study.
Age. Older dogs were more likely to be affected.
Breeds. Boxers, Rottweilers, Maltese and Poodles stood out. Some of these breeds are already known to be prone to dry eye.
Timing. All four definite cases were found during treatment, or within two days of finishing. Some possible cases were found weeks later. The authors say linking late cases to the drug “needs further investigation.”
Our note: The paper doesn’t say whether a tear test before or during a course of this antibiotic is standard. We don’t advise one. Ask your vet.
3. What the study can’t tell you
Missed cases. Dogs seen at another practice afterwards may have been missed. The authors also say some cases may have been misclassified because notes lacked detail.
Few definite cases. With only four definite cases, the risk factors are uncertain.
Figures that differ. The abstract gives 2,243 treated dogs; the breed table describes 2,141.
Our note: An earlier small study the paper cites found a much higher rate, 15.2% in 33 dogs. We can’t explain the gap from what we read.
4. If your dog is prescribed an antibiotic
- Ask your vet whether it carries any risk to the eyes.
- Watch the eyes during the course, especially in older dogs and breeds prone to dry eye.
- Report changes promptly. Dry eye caught early is easier to treat.
Our note: These points are ours, not the paper’s, including “caught early is easier to treat”.
→ “Finish the Course”: Antibiotics for Dogs
5. What we could not verify
| Commonly said | What we found |
|---|---|
| “This antibiotic often causes dry eye” | Rare in this study. Definite cases were 0.19%. |
| “Higher doses cause dry eye” | Not shown. Dose wasn’t linked to dry eye here. |
| “Dry eye can appear months later” | Not settled. The authors say late cases need more study. |
Sources
- Hardefeldt LY, et al. Retrospective cohort study on the development of keratoconjunctivitis sicca in dogs treated with [drug name omitted]: a VetCompass Australia study. J Vet Intern Med 2026: VetCompass Australia records, 2,243 dogs, 2012 to 2022. Australian Research Council funding
Always confirm with your vet before acting on anything on this page.