Basically, I just want to know if it is safe and cost effective to use human shampoo to wash my poodle.
The most common reason not to use human shampoo on a dog is that dogs have different pH levels than humans, as explained by petMD.
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.
A professional dog groomer, Barbara Bird, performed an observational study in 2011 on pet and human shampoos, ultimately collecting pH levels for 60 pet shampoos and 45 human shampoos.
the human shampoo products are formulated in the more acidic range, as expected. However, it also shows how few of the pet shampoos are formulated in the range they would be expected to fall – above 6.5. Forty of the sixty pet shampoos, two-‐thirds of the sample tested at pH of 6.5 or less, in the acidic range along with 89% of the human shampoos.
She refers to two studies that look at the effect of acidifying skin:
Matousek, J, Campbell, KL, Kakoma, I, Solter, PF, Schaeffer, DJ, Evaluation of the effect of pH on in vitro growth of Malassezia pachydermatis, Can J Vet Res>v.67(1); Jan 2003.
Matousek JL, Campbell KL, Kakoma I, Schaeffer DJ. The effects of four acidifying sprays, vinegar and water on canine cutaneous pH levels. J Am Anim Hosp Assoc. 39:29-‐33 (2003)
and concludes with:
There is no scientific evidence that shampoo having a pH of 5.0-‐6.0 is harmful to pet skin. In fact, many pet shampoos share that pH range with human shampoos. There are, however, good reasons to use a good pet shampoo on dogs: Shampoos formulated for canine hair are designed to clean well and are often geared toward specific jobs or coat types. Human shampoos are designed for daily or weekly use and may not clean a dirty dog well. They are also mostly formulated to soften hair, which may not be desirable when scissoring a Bichon or maintaining a terrier coat. Human hair shampoos are less likely to have ingredients for whitening, promoting deshedding, or serious deodorizing.
So, basically, it seems to be safe, but it may not be the most effective type of shampoo for your dog's coat (you may need to wash him several times with human shampoo to get him clean, or a dog shampoo may contain whiteners that will make him look better).
Personally... I absolutely HATE dog shampoos. Not only are they very expensive but have very strong smells, I admit I'm very sensitive to smells but that's nothing comparing to what the dog is smelling. I agree with the comments on PH levels, and having said that most dog shampoos are loaded with detergent instead of gentle glycerin based soaps which would be PH neutral. To wash my dogs I get natural, scent free soap bars from a health store; and feel free to splurge on a good quality bar because, unlike the liquid shampoos, it will last and last and last. As an added bonus I found it much easier to use a bar of soap to wash both my giant mutt and a pocket sized min-pin, just rub the bar all over their coats, give the doggies a good massage, rinse and prepare for a shake-off :)
Yes it is, in theory. The basic difference between human and dog shampoo is PH (though there is some controversy about PH levels). There are multiple considerations and options with shampoos. You can do a bunch of research and consider all the alternatives but in the end you will find all shampoo is liquid detergent.
If you are not bathing often, and your are not buying shampoo with a lot of extras, anything will do. If your dog is extremely dirty you might consider a dish detergent.