Skin is the biggest organ of the body. A US National Institutes of Health (NIH) lesson on skin lists its jobs: it covers and protects the body, keeps germs out, makes the pigment that gives it color, helps hold body temperature steady and gives the sense of touch [1]. Dogs and cats share this basic plan, with some differences in their hair and glands that this page points out [2].
The skin is built in three main layers: the epidermis on the outside, the dermis in the middle and a deep fatty layer underneath [1]. Hair, claws and glands grow out of it.
This page explains each part in plain words and links to our guides on problems that involve it.
The epidermis: the outer layer
The epidermis is the visible layer, the one you see when you part the coat [1]. It is the first barrier against germs and other things from outside [1]. Dogs and cats have a thinner epidermis than people do [2].
Skin cells that renew themselves. New skin cells form at the bottom of the epidermis and move up to replace the old cells that flake off the surface [1]. When that renewal speeds up or goes wrong, the coat can fill with flakes. For flaking, see dog dandruff and dry, flaky skin. For an inherited scaling disease, see ichthyosis in dogs.
Color cells. Some skin cells make melanin, the pigment behind skin color, which soaks up part of the sun’s harmful rays but does not block them all [1]. For loss of skin color, see vitiligo in dogs and cats. Pale, thinly haired skin gets the least protection; in cats, see sunburned ear tips in cats.
Immune cells. The skin also holds immune cells that fight germs [1]. When the skin reacts to something it touches, a rash can follow. See contact dermatitis in dogs and cats.
Touch. Special nerve cells let the skin sense texture, pressure and temperature [1].
The basement membrane zone: the link between layers
A thin band of structural proteins, called the basement membrane zone, anchors the epidermis to the dermis below it [3]. If this anchor is weakened, for example when the immune system wrongly attacks those proteins, the layers can pull apart. That shows up as small fluid blisters (vesicles), larger blisters and later deep sores [3]. These autoimmune blistering diseases are rare and were first described in dogs [3]. For an inherited blistering disease of puppies and kittens, see epidermolysis bullosa in dogs and cats.
The dermis: the middle layer
The dermis lies under the epidermis and carries what the outer layer needs [1].
- Blood vessels: the dermis holds the skin’s blood vessels [1], and blood flow through the skin is one of the ways a body sheds heat [4].
- Nerves: nerve endings in the dermis pick up touch, pressure and temperature [1]. Itch travels through skin nerves too. For itching, see why is my dog so itchy and itchy cats and overgrooming.
- Glands: the oil and sweat glands sit in this layer [1].
- Strength: the dermis gives skin its strength and stretch. For skin that tears or stretches too easily, see cutaneous asthenia in dogs and cats.
Hair, glands and claws
Hair grows from follicles, small pockets in the skin, and the follicles also help wounds heal [1].
Hair follicles. A person’s scalp hairs mostly grow one per follicle. In dogs and cats, follicles usually come in groups: one main follicle is joined by several smaller ones, so a single opening can carry a stiff guard hair plus a tuft of softer undercoat hairs [2]. Dogs and cats also have more follicles packed into each patch of skin than people do [2].
Shedding. Each hair grows, rests and then falls out, and the shedding step is part of a normal cycle [2]. In dogs, how long hairs grow and how many are resting at once depends on breed, coat type, body area, season, age and hormones [2]. In cats, body area and day length shape the cycle [2]. That is why many pets shed more at some times of year. For normal shedding versus hair loss, see hair loss in dogs and hair loss in cats.
The hair coat. The coat shields the skin and affects how well a pet copes with heat. Dogs with a thick coat are less able to cool down in hot weather [4].
Oil glands. Oil (sebaceous) glands empty into the hair follicles [1]. In cats, glands in the cheeks give off scent signals that the cat leaves on objects when it rubs its face on them [5]. For a disease that targets these glands, see sebaceous adenitis in dogs.
Sweat glands. Dogs and cats sweat very little compared with people. Dogs get rid of extra heat mainly by panting, which lets moisture evaporate from the nose and airways [4]. Cats have sweat glands in their foot and toe pads [6].
Claws. Claws grow out of the skin as well. See nail and nail-bed problems in dogs and cats.
The subcutis: the inner layer
The deepest layer, called the subcutis or hypodermis, stores energy as fat and ties the skin to the muscles and bones beneath it [1]. For soft fatty lumps, see lipomas in dogs.
When to see your vet
See your vet if your dog or cat has:
- itching, licking, scratching or chewing of the skin;
- hair loss, flaking, blisters or a change in skin color;
- a new lump, or skin that tears easily.
To learn what your vet may test for, see how vets diagnose skin problems in dogs and cats.
FAQ
Do dogs and cats sweat?
Only a little. Dogs cool themselves mainly by panting [4]. Cats have sweat glands in the pads of their feet [6]. Neither can cool down by sweating the way people do, so keep them out of the heat.
Why do dogs and cats shed more at certain times of year?
Hair grows and falls out in cycles. Season and day length affect those cycles in both dogs and cats, so many pets shed more heavily at some times of year [2].
Why does my cat rub its face on things?
Glands in a cat’s cheeks make scent signals. When a cat rubs its cheek on furniture, doorways or people, it leaves that scent behind [5].
The bottom line
Dog and cat skin has three main layers: the epidermis on the outside, the dermis in the middle and the subcutis on the inside, with a thin basement membrane zone joining the first two. Hair, oil and sweat glands and claws grow out of the skin. Each part can have its own problems, so see your vet when the skin, coat or claws change.
This article is for general information only and does not replace advice from your veterinarian. If your pet has a skin problem, see your vet.
Sources
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health. Health Lesson: Learning About Skin. https://www.niams.nih.gov/health-topics/educational-resources/health-lesson-learning-about-skin
- Seo J, Yun JH. Alopecia management from a comparative perspective: pharmacological and pharmaceutical insights in humans, dogs, and cats. Frontiers in Veterinary Science. 2026. Open access (CC BY 4.0). https://doi.org/10.3389/fvets.2026.1907027
- Bizikova P, Olivry T, Linder K, Rybnicek J. Spontaneous autoimmune subepidermal blistering diseases in animals: a comprehensive review. BMC Veterinary Research. 2023. Open access (CC BY 4.0). https://doi.org/10.1186/s12917-023-03597-1
- Hall EJ, Carter AJ, O’Neill DG. Dogs Don’t Die Just in Hot Cars: Exertional Heat-Related Illness (Heatstroke) Is a Greater Threat to UK Dogs. Animals. 2020. Open access (CC BY 4.0). https://doi.org/10.3390/ani10081324
- Crump E. Effectiveness of F3 feline facial pheromone analogue for acute stress reduction within clinical veterinary practice. Veterinary Evidence. 2023. Open access (CC BY 4.0). https://doi.org/10.18849/ve.v8i4.669
- Munger BL, Brusilow SW. An electron microscopic study of eccrine sweat glands of the cat foot and toe pads. The Journal of Biophysical and Biochemical Cytology. 1961. PubMed abstract. https://pubmed.ncbi.nlm.nih.gov/14477204/