Ozone water for dogs with MRSP - what a 2025 study actually found. (and what it means for your furbaby)

MRSP — short for methicillin-resistant Staphylococcus pseudintermedius — is one of the trickiest bacterial infections dog owners and vets face today. It’s a version of a common dog bug that won’t respond to typical beta-lactam antibiotics, and many MRSP strains are resistant to multiple drugs. That makes safe, effective topical treatments (things you can put on the skin) especially attractive, because they can reduce the bacterial load without driving more antibiotic use. Recent research from Matsuda and colleagues (2025) tested whether ozonated water (also called aqueous ozone) could safely and quickly reduce bacteria on dog skin — and the results are promising. Here’s a friendly summary of what they did, what they found, and what it realistically means for pets with MRSP.

What is MRSP and why is it a problem?

S. pseudintermedius normally lives on dog skin and in their noses. Sometimes it causes infections (pyoderma, infected wounds, ear infections). When the strain carries the gene for methicillin resistance (MRSP), many routine antibiotics become ineffective. MRSP has been reported worldwide and tends to be multi-drug resistant, which creates treatment headaches and infection-control concerns for families and clinics. Diagnosis usually relies on culture and antibiotic susceptibility testing so the vet can choose the best medication when systemic antibiotics are needed.

What did the Matsuda 2025 study ask?

The research team wanted to answer two practical questions:

1. Does ozonated water kill bacteria on dog skin — and how well?
2. Does it harm the skin’s barrier or skin cells if used repeatedly?

They compared three things: purified water (as a negative control), ozone water at 3 mg/L, and two strengths of sodium hypochlorite (the active disinfectant in diluted bleach) at 0.005% and 0.05%. Sodium hypochlorite is a known, widely used topical disinfectant — but at effective concentrations it can be harsh on skin cells. The researchers used healthy beagles to test immediate antibacterial effect and measured skin barrier markers after two weeks of daily application. They also tested how the solutions affected cultured canine skin cells in the lab.

How the study was done

• Animals: Four beagles for the short-term antibacterial test; six beagles for the two-week skin-barrier test.
• Antibacterial test: The researchers applied one of the test liquids to skin and collected skin swabs 5 minutes later to see how many bacteria remained.
• Barrier test: For two weeks, they applied the products once daily and tracked two standard measures of skin health: transepidermal water loss (TEWL) (how much water evaporates through the skin — higher is worse) and skin surface hydration (SSH) (how moisturised the skin is).
• Cell test: They also exposed canine epidermal keratinocytes (skin cells grown in a dish) to each product for 5 minutes to check whether cell growth (proliferation) was harmed.

What they found — the short version

• Ozone water (3 mg/L) significantly reduced skin bacteria within 5 minutes. The effect was comparable to the stronger sodium hypochlorite (0.05%).
• Neither ozone water nor the bleach solutions made TEWL or skin hydration worse over the two weeks — meaning no measurable short-term damage to the skin barrier.
• But there was an important difference in cell safety: the 0.05% sodium hypochlorite completely stopped keratinocyte proliferation in vitro (it was toxic to the cells), whereas ozone water did NOT inhibit keratinocyte proliferation. In other words, the ozonated water killed bacteria but didn’t appear to kill the skin cells in the lab test.

Why that matters for dogs with MRSP

• MRSP is often resistant to antibiotics, but oxidation kills bacteria irrespective of antibiotic resistance. Ozone acts by oxidizing (damaging) bacterial cell structures and can also disrupt biofilms that protect bacteria. That makes ozone a plausible topical option against MRSP colonization on the skin or in superficial wounds. The Matsuda study shows the idea isn’t just theoretical: ozone water lowered skin bacteria quickly in live dogs.
• Safety is key. Some disinfectants that kill bacteria also damage skin cells or dry out the skin with repeated use. The Matsuda team found no short-term harm to skin barrier measures and no toxicity to canine skin cells from ozone water — unlike the stronger bleach solution tested. That suggests ozone may be gentler when used correctly.

Important limitations

This was a small, preliminary study. A few things to keep in mind before you start dousing your dog in ozone water:

• The dogs in the study were healthy. The research did not test ozone water on dogs with MRSP lesions or deep wounds, so we don’t yet have direct clinical outcome data (e.g., “did the infection clear faster?”).
• Sample size was small (4–6 dogs per test), and the antibacterial effect was immediate (5 minutes after a single application). That shows rapid killing, but not whether repeated use resolves MRSP infections or prevents recurrence.
• Ozone is an oxidant — safe use depends on concentration and exposure time. Inhaling ozone gas (not dissolved water) can irritate lungs; unregulated DIY ozone equipment can be unsafe. The study used controlled, veterinary grade ozonation (3 mg/L).

Practical takeaways for pet owners

1. This study supports the idea that ozonated water could be a safe, effective topical disinfectant for dog skin. It reduced bacteria quickly and didn’t harm skin cells in lab tests.
2. For MRSP, think of ozone water as a promising adjunct — not a replacement — for veterinary care. If your dog has confirmed MRSP, the vet still needs to assess whether systemic antibiotics, topical medications, or wound care are required. Ozone water might be used alongside those therapies to reduce surface bacteria.
3. Talk to your veterinarian before trying ozone. Ask about validated devices, correct concentrations (the study used 3 mg/L), and safe application methods. Avoid inhaling ozone gas and don’t use unverified DIY ozone generators around pets.
   

Bottom line

Matsuda et al. (2025) provide encouraging early evidence that ozonated water (3 mg/L) can quickly reduce skin bacteria on dogs without damaging the skin barrier or killing skin cells — at least in healthy animals under controlled conditions. For MRSP, which is resistant to many antibiotics, aqueous ozone is a scientifically plausible topical treatment. More clinical trials directly on infected animals are needed, but this study is a solid step toward safer, non-antibiotic options for managing troublesome canine skin infections. If you’re interested in exploring ozonated water for your dog, take the next step with your veterinarian — they’ll help match the science to your dog’s specific situation.

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Key references

Matsuda, A, Ano, T, Nakamura, Y, Itoi, T, Arai, K, Kutara, K, Sugimoto, K & Maeta, N 2025, ‘Ozone water has antibacterial properties in dogs without skin barrier impairment’, Veterinary Dermatology, vol. 36, no. 3, pp. 283–290, doi:10.1111/vde.13339

van Duijkeren, E, Catry B, Greko C, Moreno, M, Pomba, MC, Pyorala, S, Ruzaukas, M, Sanders, P Threlfall, EJ, Torren-Edo,  & Torneke, K 2011, ‘Review on methicillin-resistant Staphylococcus pseudintermedius’, Journal of Antimicrobial Chemotherapy, no. 66, pp. 2705–2714, doi:10.1093/jac/dkr367