Or: why you shouldn't bathe your dog with human shampoo?
What does skin do?
As with people, skin is the largest organ in a dog's or cat's body. It provides a protective barrier against the environment, regulates temperature and is responsible for the sense of touch. Depending on species and age, skin can make up 12 to 24% of a dog's or cat's body weight.
What is the structure of skin?
It has 3 main layers: the epidermis, or outermost layer, the dermis (the middle layer) and the subcutis (the innermost layer). Other important parts of the skin include skin appendages (such as hair and nails), and subcutaneous muscle, fat and sweat glands.
What are the differences between a dog's skin and a human's?
Plenty. The most important anatomical and physiological differences are:
A dog's coat grows in bundles, while human hair grows as individual strands and grows continuously, unlike a dog's hair, which grows in cycles.
When a dog's or cat's hair reaches the length set by that individual animal's genes, it stops growing and then dies off.
A dog's skin has two types of glands that produce fluid – apocrine and eccrine (merocrine). Apocrine glands, which produce sweat in people, have two other functions in dogs – they help bind together the outer layer of the epidermis, and they secrete the pheromones that give a dog its distinctive body scent. The eccrine glands in the paws produce watery secretions similar to human sweat. These glands secrete when a dog is nervous or stressed, and they also help improve grip for fast running.
What's the pH of our pet's skin?
The pH value of a dog's skin is around 7.5, a cat's around 6.5, while human skin is around 5.5, on the standard pH scale of 0 to 14. A dog's skin is very close to neutral pH and significantly more alkaline than human skin, so the type of shampoo you use on your dog needs to be far more pH-neutral than the typical pH of a shampoo formulated for human hair. Shampoos for people sit at pH 4.5-5.5, which makes them far more acidic and, ultimately, very irritating for a dog's coat and skin. Here are some examples of the pH levels of products some people use on dogs:
- Soap - pH 9.5
- Johnson & Johnson baby shampoo - pH 5.5
- Bicarbonate of soda - pH 8.3
- Vinegar - pH 2.2
A dog's skin is the most alkaline of all species, which makes it an ideal breeding ground for bacteria (also known as skin infections). If the pH is disrupted, inflammation and infections can occur, caused by drying out and erosion of the epidermis (the outermost layer of the skin).
Skin pH:
- Human - 4.8
- Guinea pig - 5.5
- Horse - 6.3
- Pig - 6.3
- Cat - 6.4
- Dog - 7.4
A dog's epidermis is only 8-10 cell layers thick, while a human's is 18-20 cell layers thick! A dog's skin is thicker overall, but the epidermis itself is very thin and vulnerable to bacteria if the skin's pH changes.
It's important to remember that, because of these key anatomical and physiological differences in the skin, we shouldn't use cosmetics made for humans on our furry friends. There's a wide choice of products made for use on dogs, and breed, age and individual traits all matter. Because of this, don't hesitate to ask your vet or groomer for advice when choosing grooming products.
