The dog needs a bath, it's after 6 p.m. on a weekday, and you don't have any dog shampoo on hand. Let's concede that shampoo made for people will clean your dog, but the question is, is it good for your dog? This may seem like a quibbling question, but it can actually have far-reaching consequences.
We'll start with the how's of people skin and dog skin. A highly important component of skin is what is called the acid mantle. This is a lightly acidic layer that covers the skin, serving as a barrier to protect the porous topmost layer of the skin, the stratum corneum, from environmental contaminants such as bacteria and viruses. The stratum corneum is responsible for keeping the outer body well hydrated, by absorbing water and not allowing excessive evaporation to occur. When we bathe, using soaps and shampoos, we wash away this layer of acidic oil. This is why most human shampoos and soaps are formulated with moisturizers to replace the protective layer that has been scrubbed away, at least until the skin is able to replenish itself around 12 hours later. If the stratum corneum is left stripped and unprotected, it is open to a host of microorganisms, which may present as dry, flaky skin, irritated, peeling skin, or as a rash of itchy bumps.
The acid mantle can also be defined as the relative pH balance of the skin. The pH scale ranges from 0 to 14, with levels less than 6.4 considered high acidity, and levels more than 6.4 considered high alkalinity. The normal range of skin pH levels for humans is 5.2 to 6.2, which means it tends to be on the acidic side, and shampoos and skin products are formulated specifically to maintain this balance.
Now consider the relative pH balance for dogs. Depending on breed, gender, climate, and the anatomical size on the dog, the pH levels range from 5.5 to 7.5, tending toward a more alkaline concentration. Therefore, if a shampoo that is formulated for human skin is used on a dog, the dog's acid mantle will be disrupted, creating an environment where bacteria, parasites, and viruses can run rampant. Unknowingly, many pet owners will repeat washings of their dogs because of the smell caused by a proliferation of bacteria, making the problem worse as the skin's acid mantle/pH level becomes more imbalanced. Additionally, if the shampoo makes the skin feel dry, your dog will scratch at its skin, creating abrasions for bacteria to invade. It quickly becomes a vicious cycle.
Just as you would look for a shampoo that helps maintain the pH balance of your own scalp, you should also concentrate on finding a shampoo with a pH balance that is specifically balanced for a dog's skin. Dog shampoos should be in the neutral range, around 7. Many shampoo manufacturers will include the pH level on the label, but at the very least, they will clearly state that the shampoo is pH-balanced for dogs.
Do read the labels, making sure that there are no artificial fragrances or colors added to the shampoo. Your dog may be a big strong guy and still have sensitive skin. Look for natural skin moisturizers like vitamin E, aloe vera, honey, and tea tree oil. Fragrances to look for should be natural; chamomile, lavender, eucalyptus, and citrus are some examples of clean, pleasant fragrances, some of which also do double duty as insect repellents. If you can find organic, even better, but don't rely on the front label alone. Again, read the ingredients list.
Your dog doesn't need to be washed with shampoo on a regular basis. A good cleaning every few months is all your dog needs (you can give water baths in between), so you can splurge a little on a shampoo with quality ingredients when you weigh the overall time you will be using it. One bottle can last a year, even if you only shampoo your dog once a month. So go for the good stuff, and you won't mind when your dog places his paws on your lap for a friendly hug.
Image: Ginny / via Flickr