Bathing, Ear Cleaning and Coat Care: What Dermatology Actually Says
How often should you bathe a dog, or clean its ears? One small study and some expert advice is most of the evidence. What it says, and where it stops.
Written by thecanineledger
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If your dog’s ear is red, swollen, smelly, painful to touch, or has discharge, or your dog keeps shaking its head or tilting it, see a vet before you clean it. The Merck Veterinary Manual owner guide warns that “Even products normally safe in healthy ears can irritate inflamed ears.”
Our note: The signs are general signs of ear disease. The advice not to clean before a vet visit is ours, based on the manual’s warning.
The most specific bathing advice we found comes from a 2013 study of eight dogs. Its authors concluded that “bathing the dog with canine commercial shampoo was appropriate every 5 or 8 days” (Yu et al., Journal of Veterinary Clinics 2013).
While that sounds precise, the study didn’t bathe whole dogs, and most bathing advice online has no study behind it at all. This page sets out what we found on bathing, ear cleaning and brushing, and where the evidence runs out.
1. Bathing: how often
What the eight-dog study did. Researchers applied a dog shampoo to patches of skin on 8 dogs: “every other day, 5 days, and 8 days on different sites”. They compared those patches with a patch treated with saline.
What changed. Only the every-other-day patches changed significantly. The authors read those changes as signs that “the frequent use of canine commercial shampoo cause abnormalities of the skin barrier function”.
What it doesn’t show. It tested one shampoo, on small patches, in healthy dogs. It didn’t test whole-body baths, dogs with skin disease, or different coats. Eight dogs is a very small study.
Expert advice differs. The Merck Veterinary Manual owner guide says: “Bathe your dog with pet shampoo about once a month, depending on the season, or whenever your dog’s coat gets very dirty or smells bad.” It cites no study for this.
Our note: The study’s “every 5 or 8 days” and the manual’s “about once a month” don’t match, and neither is a strong basis for a rule. If your dog has skin disease, follow your vet’s plan.
→ The Itchy Dog: Allergies, Atopic Dermatitis, and What Actually Helps
2. Ear cleaning
Healthy ears. We found no study of whether routine cleaning helps healthy ears. The manual suggests regular cleaning for some dogs: “If your dog often develops ear infections, your vet may ask you to clean the dog’s ears regularly.”
How to clean, if your vet says to. The manual’s first rule: “Don’t use anything that pushes debris deeper in the canal.” It adds: “Don’t use cotton swabs.”
Does cleaning help an infection? A 2024 trial treated 40 infected ears in 23 dogs with the same medicine. Half the ears were cleaned first, and half were only wiped with gauze (Corb et al., Veterinary Dermatology 2024, abstract).
- The authors found that “Both groups achieved successful outcome regardless of cleaning.”
- But “Ear cleaning may be more important when rod-shaped bacteria are present.” Only a vet’s test of the ear discharge can show those bacteria.
Swimmers. The manual suggests “drying agents as recommended by your veterinarian for dogs that swim frequently.”
Our note: The 2024 trial was small and covered ears that were already infected. Most owners clean ears that aren’t.
→ Ear Infections: Why They Keep Coming Back
3. Brushing and mats
Why brush. The manual says brushing removes loose hair and prevents mats, and that “Matted hair can irritate the skin and lead to infections.”
Removing mats. “Don’t use scissors to remove mats, because it’s easy to accidentally cut the skin.” The manual suggests clippers made for pets instead.
What we didn’t find. We found no study of how often to brush different coat types. We also found no study testing whether shaving a double coat makes a dog hotter or cooler.
Our note: We found no study on shaving double-coated dogs in summer, either way.
→ The Everyday Care Most Dogs Need, and the Rules of Thumb Nobody Can Source · → Nail Trimming: Which Dogs Need It Most, and Why So Many Hate It
4. What we could not verify
| Commonly said | What we found |
|---|---|
| “Bathe every 4–6 weeks” | No source found. One small study suggested 5 or 8 days. A vet manual says about once a month. |
| “Bathing too often dries the skin” | Possibly. In one 8-dog study, shampooing every other day changed the skin barrier. Whole-body bathing wasn’t tested. |
| “Clean your dog’s ears every week” | No study for healthy ears. The manual suggests regular cleaning mainly for dogs prone to infections. |
| “Always clean before ear drops” | Not always needed. In one small trial, infected ears healed as well without cleaning, except perhaps for some bacteria. |
| “Cotton buds are fine for ears” | No. The manual says not to use them. |
| “Shaving a double coat makes dogs hotter” | Not tested. We found no study either way. |
Sources
- Corb E, Griffin CE, Bidot W, et al. Effect of ear cleaning on treatment outcome for canine otitis externa. Vet Dermatol 2024. ⚠️ abstract read. Randomised trial, 40 ears in 23 dogs
- Yu JW, Shin HJ, Bae S, et al. Functional Assessment of Frequency of a Commercial Shampoo for Normal Canine Skin. J Vet Clin 2013: experimental study, 8 dogs. Article in Korean with an English abstract; we read the English abstract
- Antinoff N. Routine Health Care of Dogs. Merck Veterinary Manual, pet owner version. Full review July 2025, last updated September 2026. ⚠️ not peer-reviewed. Expert reference
- Roman N. Ear Infections and Otitis Externa in Dogs. Merck Veterinary Manual, pet owner version. Full review April 2026. ⚠️ not peer-reviewed in the journal sense; the page says it was reviewed by a second vet. Expert reference
Always confirm with your vet before acting on anything on this page.