Picture this: your dog’s pawing at one eye, maybe holding it half shut, maybe there’s a bit of gunky discharge crusting in the corner. You crouch down to get a proper look, and somewhere in the back of your mind a voice pipes up, your mum’s, or your nan’s, or her mum’s before that, all saying the same thing: bathe it in salt water, that’ll sort it out. It’s advice that’s been passed down through generations, tried and (eye) tested. And it’s one of those old wives’ tales that’s almost right, which is exactly why it’s worth a closer look before you reach for the salt shaker.
The bit that’s actually true
Turns out Grandma wasn’t just making a spectacle of herself. There’s real clinical logic behind the idea. Saline genuinely is the right tool for a sore or irritated eye. It’s not folklore, it’s the actual clinical standard. Physiological saline (a 0.9% salt solution, matched to the salt concentration of your dog’s own tears) is the reference solution traditionally used to rinse eyes after an accidental chemical spill and as a general ophthalmic wash. If your dog’s had shampoo, dust, pollen, or some mystery backyard substance splashed in their eye, veterinary advice is genuinely to flush the eye for 20 to 30 minutes using sterile saline or tepid water. “Tepid” just means lukewarm, roughly body temperature, which is much less of a shock to an already-irritated eye than water straight from the cold tap (Veterinary Vision Center, n.d.). Use a gentle, low stream rather than a jet. Avoid high-pressure spray devices, as this can damage the cornea, the clear dome at the front of the eye, no need to make a bigger production of it than necessary (Veterinary Vision Center, n.d.).
So no, the instinct isn’t wrong. The problem is what happens between “I want to make saline” and “I’ve actually made saline,” and that’s where things start to look a little cloudy.
Here’s where it goes sideways
Getting the salt ratio right isn’t the hard part. It’s getting it sterile, and staying sterile, that trips people up. The American Academy of Ophthalmology has fielded this exact question from the human side, and their answer is blunt: outside a genuine emergency, don’t irrigate eyes with tap water or homemade saline. Tap water has less salt than natural tears and tissue, which can be irritating and even damage the surface cells of the eye (American Academy of Ophthalmology, n.d.). And it’s not just about irritation. Using tap water or homemade saline in the eye has been linked to serious eye infections, including infection with Acanthamoeba, a nasty little organism that’s genuinely hard to treat once it takes hold (American Academy of Ophthalmology, n.d.). Not exactly a sight for sore eyes.
Acanthamoeba isn’t some exotic lab hazard. It’s a free-living protozoan found pretty much everywhere: dust, soil, air, tap water, even beach sand. And here’s the eye-opening bit: it’s not a theoretical overseas risk. UNSW researchers testing bathroom taps in greater Sydney found around one third of tap water sampled from bathroom sinks contained Acanthamoeba, and a follow-up study of NSW coastal water found it present at every site tested, with over half of samples positive at the most urbanised location (UNSW Sydney, 2023). It’s genuinely in our water, right now, and there’s no reason to think Brisbane taps see things any differently.
And for the “just boil the water” crowd, boiling doesn’t necessarily solve the problem if the container, the salt, or your hands introduce contamination afterward, or if the solution sits around collecting bacteria over the following days. A watertight recipe on paper doesn’t always hold up in practice.
Does this actually happen in dogs?
Fair question, and worth answering honestly: it’s under-studied, but it’s not nothing, and it’s been a genuine blind spot (sorry, had to) in small-animal medicine. Most vets, seeing keratitis (that’s inflammation of the cornea, showing up as redness, cloudiness, discomfort, or excess tearing) in an animal, think bacteria, viruses, or fungi first. But there’s growing evidence of a link between Acanthamoeba and keratitis in animals, and the condition is likely under-diagnosed but potentially common in pets (Cooper, Cowmeadow and Elsheikha, 2021). A separate study screening dogs with eye disease at a veterinary teaching hospital in Korea found Acanthamoeba present in about 5.3% of the dogs tested, in dogs with and without keratitis, so it’s not a slam-dunk cause-and-effect, but it confirms the organism is genuinely circulating in the dog population, not just a human contact-lens problem (Lee et al., 2024).
So what do you actually do?
Nothing complicated, no need to squint at a complicated protocol here.
- Skip the DIY kitchen recipe. Sterility at home is genuinely hard to guarantee, and the eye is one of the least forgiving places on the body for that mistake.
- Grab a bottle of preservative-free 0.9% sterile saline from the chemist. It’s cheap, shelf-stable, sterile until opened, and it’s the same concentration as the homemade version, minus the risk. Worth a spot in the first aid kit alongside the bandages and tick removers (RSPCA Queensland, n.d.).
- Tap water is fine, but only for a genuine emergency. Chemical splash in the eye (cleaning products, garden chemicals)? Flush immediately with whatever clean water is on hand and call your vet straight away. That’s an exception, not a routine strategy.
- Get it seen, sooner rather than later (pun very much intended). Eyes can go from mildly irritated to seriously compromised in a matter of hours, not days. A scratch or ulcer that looks minor today can threaten vision by tomorrow if it’s left untreated. When in doubt, don’t wait it out.
If your dog’s eye is red, weeping, or they’re squinting and it’s not settling down quickly, book a house-call and I’ll come to you.
References
American Academy of Ophthalmology (n.d.) Is it OK to wash your eyes out with tap water? Available at: https://www.aao.org/eye-health/ask-ophthalmologist-q/is-it-ok-to-wash-your-eyes-out-with-tap-water (Accessed: 2 July 2026).
Cooper, E., Cowmeadow, W. and Elsheikha, H.M. (2021) ‘Should veterinary practitioners be concerned about Acanthamoeba keratitis?’, Parasitologia, 1(1), pp. 12–19. Available at: https://doi.org/10.3390/parasitologia1010002 (Accessed: 2 July 2026).
Lee, S., Alkathiri, B., Jung, J.S., Kang, N., Hwang, J., Park, S.E., Hong, Y., Park, K.M. and Lee, S.H. (2024) ‘Molecular detection and characterization of Acanthamoeba infection in dogs and its association with keratitis in Korea’, Parasites, Hosts and Diseases, 62(1), pp. 139–144. Available at: https://doi.org/10.3347/PHD.23112 (Accessed: 2 July 2026).
RSPCA Queensland (n.d.) Pet First Aid Advice from Greencross Vets. Available at: https://www.rspcaqld.org.au/blog/pet-care/pet-first-aid-advice-from-greencross-vets (Accessed: 2 July 2026).
UNSW Sydney (2023) Microorganism that causes rare but severe eye infections detected in NSW coastal areas. Available at: https://www.unsw.edu.au/newsroom/news/2023/08/microorganism-that-causes-rare-but-severe-eye-infections-detecte (Accessed: 2 July 2026).
Veterinary Vision Center (n.d.) What toxins can damage your pet’s eyes? Available at: https://veterinaryvisioncenter.com/what-toxins-can-damage-your-pets-eyes/ (Accessed: 2 July 2026).
