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What Is Lurking in Your Dog's Water Bowl?

Data shows that what your dog's water bowl is made of may affect his health.

Creative Commons CC0 license
Source: Creative Commons CC0 license

Since I am a psychologist, I seldom write about veterinary matters that impact dogs unless there are some human or canine behavioral issues involved. Thus, I did find myself called to write about the raw food movement because it appeared to me that some dog owners who insisted on a raw food diet, despite the fact that most of the major veterinary associations have recommended against it, might be showing symptoms consistent with orthorexia nervosa.

This is an eating disorder that was studied by American physician Steven Bratman, who was concerned that an obsession with healthy food could, paradoxically, lead to unhealthy consequences. Only here, the concern was with healthy food for dogs (click here to read my article about that). However, this time I find myself writing about a situation where people seem to show too little concern for the health of their dogs.

My current interest was stirred by the fact that this week I received two separate communications from correspondents focusing concerns about our dogs' water bowls. The first was a query about whether I was aware of a 2011 study conducted by NSF International. This study tried to assess what were the most germ-laden, dirty, and unhealthy places in our homes. Coming in fourth place (behind the kitchen sponge, kitchen sink and toothbrush holder) was our dogs' water bowl.

I must admit that I was somewhat surprised about this, although the more that I reflected on it the more sensible it began to appear. I believe that, like most people, after my dogs have their breakfast or dinner I hand wash their food bowls or toss them into the dishwasher. As for their water bowl, well it's just water, isn't it? So I make sure that it is full and when I refill it each time, I give it a quick rinse under running water and then return it to the floor. From this communication, I learned that apparently that is not enough.

The last time that I thought about my dogs' food and water bowls was when I got my Flat Coated Retriever puppy, Odin. He was sleek and black from his shiny nose to the tip of his tail. When I brought him to the veterinarian's office for his puppy shots and a general examination at the age of around nine weeks, the vet asked me what kind of dog bowls I used. When I told him the bowls were plastic, he shook his head and said, "If you want to keep his pretty nose a uniform black, you should not be using plastic."

It turns out that plastic dog bowls can cause Plastic Dish Nasal Dermatitis. It is a loss of pigment on the nose and possibly around the mouth due to the chemical p-benzylhydroquinone which is in many plastics. This substance inhibits the production of melanin, a chemical that produces dark pigment in the body. This leaves the nose and adjacent areas with ugly pink blotches.

After I left his office, I did a little bit of research and found that p-benzylhydroquinone is not the only problem chemical associated with plastic dog bowls. There have been a number of studies that have highlighted a chemical known as Bisphenol A, or BPA which made headlines a few years ago. This is a synthetic estrogen commonly used to harden polycarbonate plastics.

However, the research shows that even in the low amounts to which people are routinely exposed, it can cause serious and sometimes irreversible damage to health. The resultant harm to the body includes disruption of the endocrine system as well as the triggering of a wide variety of problems that may result in cancer, cardiovascular system damage, adult-onset diabetes, and impaired brain and neurological functions.

I thought to myself that with this type of effect on humans, just imagine what BPA could be doing to our dogs—most of whom are much smaller and therefore probably more susceptible to injury from those same low dosages.

Okay, so I knew that the plastic dog bowls I was using would have to go, but what to replace them with? I had seen a number of very pretty ceramic dog bowls. Of course, ceramic bowls can break, especially if you have a large dog bouncing around the kitchen, and ceramic shards can cut like glass and be a hazard.

However, I reasoned, that if the bowl was heavy enough, it would be less likely to be pushed around and would also be more difficult to break. Unfortunately, I learned that dog bowls do not have to be certified as safe for food use in the same way that ceramic bowls and dishes which are intended to be used by humans for food service are.

Many of these, especially those made in China, can contain lead or other harmful chemicals. In fact, a 2009 study showed that out of 400 pet products tested, a quarter of the items had detectable levels of lead, and in more than one-third of these the levels would be unacceptable if they were in a children's product (according to the standards set by the Consumer Product Safety Commission). I think by now most people know that the symptoms of slow lead poisoning are quite nasty, including kidney, renal, cardiovascular problems, and a number of neurological disorders.

In any event, that left me with one option for my dog dishes, namely stainless steel.

I hadn't thought about this choice for many years, but then I read the second piece of correspondence about dog bowls that arrived this week. It referred to a research report delivered at the 69th Annual Meeting of the European Federation of Animal Science at Dubrovnik, Croatia.

The investigators were Coralie Wright and Aisling Carroll from Hartpury College in England. They were interested not in the chemicals associated with the construction of the water bowls used for dogs, but rather in the bacterial buildup which occurs and how this interacts with what the dog bowl is made of.

They tested plastic, ceramic, and stainless steel water bowls and found that the plastic bowls had the greatest accumulation of bacteria. This probably has to do with the fact that even with regular washing, scratches, nicks, and micro gouges can provide places where bacteria can breed. Scouring provides only a temporary solution, since that very process can provide more scratched and uneven surfaces that can serve as hiding places for bacteria.

The ceramic bowls also accumulated a lot of bacteria and, as in the case of the plastic bowls, several medically important bacteria were identified from ceramic water bowls, including MRSA and Salmonella. Some of these bacteria might be hiding in micro-cracks in the glaze which are sometimes invisible to the human eye. But even if there are no such cracks, this research suggests that harmful bacteria may be able to develop biofilms more successfully on the surface of ceramic materials and thus be able to multiply more quickly.

These results seem to confirm my initial choice of stainless steel as the best option for my dogs' food and water bowls. However, they do not confirm the adequacy of my lax and indifferent practice of simply rinsing out my dog's water bowls when I refill them.

According to that NSF International study, casually maintained water bowls (even stainless steel) will still show a buildup of some nasty bacteria. The one that you are most apt to notice visually is Serratia Marcescens, since it is sometimes seen in a water bowl that has not been adequately cleaned for a few days as a faint pink or brownish scum clinging to the sides of the bowl.

Even if nothing is visible to the eye, it doesn't mean that your dog's water bowl is safe. Yeast, mold, and coliform bacteria (which includes Salmonella and E. coli) have still been found to be lurking in dogs' water bowls.

So this research does seem to demand a behavioral change in the way that we care for our dogs. At the very least we should use a bit of antibacterial dish soap and some hot water to wash our dogs' water bowls before filling them up each day, or we should put them in the dishwasher to get a good sanitizing wash.

The idea that "It's just water, and since it came out of the tap it must be safe—even if it's been in the dog's bowl for a few days," is wrong. What goes on in that bowl can affect your dog's health, and if you have young kids playing around in the same spaces, those health problems can be transmitted to them as well.

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.


Wright, C., & Carroll, A. (2018). Microbiological Assessment of Canine Drinking Water and the Impact of Bowl Construction Material. Poster session presented at 69th Annual Meeting of the European Federation of Animal Science, Dubrovnik, Croatia.

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