Dear Doctor: Should Dogs be Bathed After Swimming in Natural Water?

Q: My dog is now almost a year old and absolutely loves to go in the water. There is a saltwater bay near our house that leads to the ocean, and nothing makes him happier than to splash around in it, and even swim in it. He grins from ear to ear. But should I be bathing him after each wet excursion? After all, water in a bay — or even in a stream or river — carries its own bacteria and other pathogens and may not be perfectly harmless. Also, I wonder if the salt in the water is prone to making the skin under his coat too dry. Please tell me the verdict on how often to bathe a dog who enjoys the ocean, lakes, ponds, or streams? I certainly wouldn’t go into the water without bathing afterwards.

Maisie Kirkland
Nahant, Massachusetts

A: Dear Ms. Kirkland,
Rest assured that your dog can enjoy the water as frequently as he wants without needing to be bathed with shampoo each time. The epidermal barrier on dogs’ skin along with “good” bacteria and other microorganisms on the skin’s surface will do much to keep him safe and healthy. The barrier keeps out offending microorganisms, and the good bacteria prevent the proliferation of bad ones that can cause staph infection and other problems.

Swimming often will not disrupt the action of these defense mechanisms. The epidermal barrier will remain intact, and the helpful bacteria on the skin will recover quickly. Ironically, it is harsh ingredients in detergents that compromise the ability of dogs’ skin to protect itself.

That said, if the dog romps in salt water such as the ocean or a bay, or in lakes, streams, and ponds with unknown high bacterial loads or other potential forms of dirt or contaminants, you should rinse him with fresh water from the tap afterwards. Dried salt on your pet’s skin can prove irritating, and it simply makes good precautionary sense to wash off pathogens from local waters that can make their way onto your dog’s skin. Why make his body work harder than necessary to fend off offending microorganisms? In addition, if he has a cut that you’re unaware off, that creates easier passage for unwanted substances into his body.

If you do decide to rinse your dog after a swim, you should dry him thoroughly if he has long fur that tends to stay wet for a long period of time. Persistent, lingering moisture can impair the skin’s defense mechanisms, and that (rather than just being in the water for a time each day) will predispose your dog to skin infections, says Tufts veterinary dermatologist Lluis Ferrer, DVM.

Note that while you do not need to bathe your dog with shampoo after his romps in the water, you may want to, at least sometimes. Frequent exposure to water can leave the skin prone to an overgrowth of yeast or other microorganisms that, while harmless, cause odor because of their interaction with fats on the skin’s surface. In a few cases, an inflammatory skin disease called seborrhea (similar to human psoriasis) can also be the cause of an unpleasant scent. If you dog has an odor, bathe him with an antimicrobial shampoo (for instance, those containing chlorhexidine or benzoyl peroxide), and be sure always to dry his skin adequately.

Some people have wondered, by the way, whether frequent swimming means a dog’s ears are more prone to yeast or other infection because of the dark, moist environment created in the ear canal. It’s doesn’t, says Dr. Ferrer. But drying the external part of the ear (up to the entrance of the ear canal) without using cotton tips and without introducing anything into the ear canal itself is not an unreasonable thing to do, he comments.