BY
BARBARA BIRD, CMG
BACKGROUND: We hear a lot of talk from pet shampoo
sales persons that pet groomers should beware of using human shampoos on
pets. One of the reasons given for
this warning is that pets and humans have significantly different pH of hair
and skin and that products formulated for human pH levels might be harmful to
pets.
An
excerpt from a website giving guidance to pet owners says, “Your dog’s coat and
skin is different from your own and requires different grooming products. The first step is to choose a shampoo
that has been formulated for dogs with the right pH and appropriate ingredients
for their skin. Human products are
too acidic for your dog’s skin and can strip the natural oils from the coat and
skin.” 1 Recently, this
warning has shown up on YouTube as, “The Dangers of Using Human Shampoo on
Pets.” This lecture, sponsored by
Petsmart, cites different pH balance as one of the main reasons for
concern. The citing of the
differences in pH of pet products as the rationale for admonishment against
using off-label products has begun to have the qualities of a myth. We accept as fact that there is some
huge difference between the pH pet and human products. What is the truth about pH?
WHAT IS pH? pH is the measure of the acidity or
alkalinity of an aqueous substance.
It measures the single property of producing hydrogen ions in solutions
(potential Hydrogen).
STUDY METHODOLOGY: The
author kept a journal, measuring the pH of products from the grooming salon,
corporate pet supply stores, drugstores and supermarket, and hair salons. A total of sixty pet shampoos and forty
five human shampoos were tested over a period of a year. All products were measured with
laboratory grade hydrion papers accurate to .5 pH.
This was the second study initiated by the author on this subject. In 2001, several members of a groomers’
email group participated the measurement of the pH of over 50 pet and human
products. The results were that
the pet products ranged from 2.2-7.5 pH, while the bulk of the human shampoos
tested within the 5.0-6.5 pH range.
There was a large overlap of products of both types in the 6.0 pH
range. It appeared that there was
more difference among the pet
products than between the pet and
human products.2
2011 STUDY RESULTS
The list of products tested and pH values is found in
Appendix A.
TABLE ONE: Number and Percentages of Pet and Human Shampoos
Along pH Range
pH Range
|
No. Pet Shampoos
|
% Pet
Shampoos
|
No. Human
Shampoos
|
% Human
Shampoos
|
<4.5
|
2
|
3%
|
0
|
-
|
4.5
|
0
|
-
|
4
|
9%
|
5.0
|
3
|
5%
|
6
|
13%
|
5.5
|
4
|
7%
|
11
|
24%
|
6.0
|
12
|
20%
|
12
|
27%
|
6.5
|
19
|
32%
|
7
|
16%
|
7.0
|
11
|
18%
|
3
|
7%
|
7.5
|
4
|
7%
|
0
|
-
|
8.0
|
4
|
7%
|
2
|
4%
|
8.5
|
1
|
1%
|
0
|
-
|
TOTALS N=60 100% N=45
100%
·
The range of pH of the pet shampoos was from
under 4.5 through 8.5. The human
products ranged from 4.5 through 8.0.
The pet products showed a slightly broader range of pH than the human
counterparts.
·
The average pH of the pet shampoos was 6.46 and
the human shampoo average pH was 5.84, a difference of .62 in average pH.
·
There was an overlapping area in the 6.0-6.5
range. Fifty two percent of the pet products and forty three percent of the
human products tested in this range.
Forty eight percent, nearly half, of the total pet & human shampoos
tested in the 6.0-6.5 range.
·
Twenty four percent of the human shampoos tested
at 5.5 pH, and thirteen percent tested at 5.0. Fewer of the pet products tested in this more acidic range,
with seven percent at 5.5 and five percent at 5.0. On the higher end of the scale, more of the pet products
tested at 7.0 and above than did the human products. The human products clustered at the mid-range and lower
(more acidic) and the pet products clustered at the mid-range and higher (less
acidic, more alkaline). This
grouping is illustrated in Chart Number Two below.
This interesting view is very
revealing. It clearly shows that
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. Pet MD states “Dog
shampoos should be in the neutral range, around 7”3. Only one-third of the pet shampoos
tested in the expected range of 7.0 or higher. Why is this so?
From a formulator’s view. The
cosmetic chemists who are formulating shampoos for pets are often the same
persons formulating for human shampoo manufacturers. They are dealing with the same array of ingredients. Many considerations come into play
around pH. For example, when
Ammonium Lauryl Sulfate is used rather than Sodium Lauryl Sulfate, the solution
is formulated at a lower pH to prevent liberation of Ammonia. Also, when polyquaternium conditioning
agents are added, the shampoo needs to be more acidic (typically 4.5-6.0) for
the maximum conditioning effect. 4 Thickness of a shampoo can also
be affected by the pH. The
preservative system used to protect the shampoo from contamination may have pH
constraints. For example, many of
the organic acid blends used as alternatives to parabens are effective only at
less than 6.0 pH.5 The bottom line is that the formulator needs to
arrive at a pH where the product will perform well and will be suited to
species on which it is used. It is
interesting to notice that as more manufacturers of human shampoo lines enter
the pet shampoo arena, the pet products begin to more closely resemble their
human counterparts.
Notes about the pH of canine skin/hair. The subject of the pH of canine skin
seems to be one of those where “the more we learn, the less we know for
sure.” Although it is true that
canine skin has a significantly more alkaline pH than human skin, there is no
single agreed upon pH number or specific range. Studies have been done that measure canine pH from 5.5 all
the way to 9.1. Although some
references will state the pH of the dog to be 7.5, they are just citing one
study. One thing is clear, pH of a
species exists as a range, and the pH of canine skin seems to be along a rather
wide range. In Skin Diseases of Dogs and Cats, Dr. Steven
Melman states that the pH of human skin is 5.2 to 6.2, while dog and cat skin
ranges from 6.2 to 7.2 with an average of 6.6
Small Animal Dermatology, 6th
Edition7 notes that, In a
dynamic study of skin surface pH in dogs. ((158), the following observations
were made: pH values varied at different sites on the skin and varied from day
to day; males had significantly higher pH values than females on all sites;
spayed females had significantly higher pH values at all sites than intact females;
black Labrador retrievers had significantly higher pH values than yellow
Labrador retrievers, and Labrador retrievers and miniature schnauzers were
significantly different from English springer spaniels and Yorkshire
terriers. Clearly, skin surface pH
appears to vary with site, day, coat color, sex, gonadal status, and
breed. In addition, it has been
reported that the skin surface pH of an excited dog can increase by greater
than 1 unit within 1 minute.7
This is not the only reference to the pH of the dog’s skin
varying by breed. A study by the Royal
Canin Research Center found the German Shepherd to have the most alkaline of
three breeds tested: the 18 GSD’s tested averaged 8.62 pH. Six Golden
Retrievers had an average skin pH of 7.57, and fifteen Labradors averaged 6.84 pH.8 Given that the scale is
logarithmic, the German Shepard pH was nearly one hundred times more alkaline
than the Labradors. With all of
these variables, it would seem like no one pH point would represent the proper
pH for a dog shampoo.
SUMMARY - MYTHOLOGY
OF SHAMPOO pH
A
“myth” is defined as “a widely held but false notion.”
MYTH: Human shampoos are formulated at a much more acidic pH
than pet shampoos. FALSE! Although some human products might be significantly more acidic than some pet products, more of the pet and
human shampoos share the same pH than those that differ. In this study, Forty eight per cent of the total pet
and human products shared the pH range of 6.0-6.5. That’s nearly half of the total sample.
MYTH: Using a mildly acidic shampoo is harmful to a dog that
has a mildly alkaline skin pH.
FALSE! Recent studies
suggest that acidifying the skin of dogs with bacterial and yeast infections
promotes healing of those conditions.9,10 There is no available evidence to support the notion that
mildly acidic shampoos damage canine skin.
MYTH: Using a shampoo with an acidic pH will damage or ruin
the “acid mantle “ of the canine skin.
FALSE! The acid
mantle theory proposes that the relative acidity of human skin serves as a
protective barrier against infection by cutaneous microorganisms.9 The relative alkalinity of canine
skin means that dogs don’t have an acid mantle. Matousek, et al, at the University of Illinois, state that,The relative alkalinity of canine
skin may be partly responsible for a higher predisposition to cutaneous
infections in the dog compared to other species, such as cats or humans.
MYTH: An acidic shampoo is more harsh and potentially
irritating than a shampoo of 6.5 pH or higher. FALSE! More
acidic is not more harsh. The
harshness of a shampoo has more to do with the character of the cleansing
surfactants, the detergency, than with the pH. A slightly acidic shampoo will leave the hair cuticle
tightly closed, resulting in smooth, shiny hair. Alkaline substances can be more harsh on the hair than
acidic products. A more alkaline
shampoo will lift and loosen the hair cuticle and is more suited for shampoos
for deep cleansing or color deposit.
This is why it is recommended to use a mildly acidic conditioner following
such treatment.
MYTH: A shampoo will have some long lasting effect on the
dog’s skin and hair. FALSE! There is no evidence to suggest that a
rinse-off shampoo product, or a leave-in conditioner is going to have any
prolonged effect on the pH of the dog’s skin. The natural desire of the body to restore balance will operate. Matousek, et al found that vinegar
spray reduced cutaneous pH to less than 6.0 for an average of 12 hours. Vinegar is about 2.4 pH, very
acidic.
CONCLUSION:
Concerns and warnings about shampoo pH and using a shampoo
balanced for the pH of the dog seem to be driven more by business and marketing
than by science. 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. Products for the trade allow the
groomer to custom pick the right product for a salon-worthy result. Your professional image is enhanced by
your knowledge of product science and your choice of professional pet
products.
REFERENCES
1.
Tips for Dogs with Sensitive Skin, www,petalia.com.au
2.
Bird, Barbara J., Beyond Suds and Scent:
Understanding Pet Shampoos and Conditioners, Birdzeye Press, Tucson, AZ, 2006
3.
Pet MD, Maintaining Your Dog’s Skin pH,
petmd.com
4.
Klein, Ken, Shampoo Formulation: The Basics,
Cosmetics & Toiletries, May,
2004.
5.
Weber, Klaus, New Alternatives to
Paraben-Based Preservative Blends, Cosmetics &
Toiletries Magazine, January 2005,Vol.120, No.1, p.57-62.
6.
Melman, Steven A. , Skin Diseases of Dogs
& Cats: A Guide for Pet Owners and Professionals, ,Dermapet, Potomac,
Maryland, 1994.
7.
Scott, DW, Miller, WH, Griffin, CE, Muller &
Kirk’s Small Animal Dermatology, 6th Ed., 2001, W.B. Saunders
(US).
8.
Weber, M, Royal Canin Research Center, 2003.
9.
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.
10. 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)
Originally published in eGroomer Journal, April 2012
This is a great read. I have often wondered about the validity of claims regarding 'specially ph formulated'. Many thanks.
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