The article states that, on the cellular level, all canine coats, whether described as hair or fur, are made of keratin. It also explains that dogs with fur have coats that grow to a predetermined length and then stop growing.

The breeds of domestic dog, *Canis lupus familiaris*, display a range of coat types with variation in color, texture, length, curl, and growth pattern.[9] One trait of interest is that of partial or full **hairlessness**, which is found in a small number of breeds.[9] Only two genes have been associated with **hairlessness in dogs**.[9] The first, *FOXI3*, is responsible for hairlessness in the Chinese Crested, Xoloitzcuintli, and Peruvian Inca Orchid dog.[9] The second, *SGK3*, was originally described by us as responsible for the recessive hairless phenotype in the American Hairless Terrier.[9] *SGK3* is essential for the development and maintenance of the **hair follicle**.[9]

Dermis, the layer under the epidermis, is composed by a conjunctive matrix where reticular, elastic and collagen fibers are found. It also contains epidermal appendages (**hair**, nails, sebaceous and sweat glands), arrector pili muscles and blood and lymph vessels. The hair follicles exhibit activity cycles that result in **hair formation**. Anagen is a period of active growth when a **new hair** is being formed… Telogen represents a period of follicle inactivity, when the **hair is shed** so that a new one may start to grow.

It says that the scientific term for the woolly or hairy covering of mammals is pelage, and that science makes no distinction between hair and fur; both are simply pelage.

One defining feature of particular interest is the **coat**, which is comprised of either a double- or single-layer of **hair**.[7] The top coat contains coarse guard hairs and a softer undercoat, similar to that observed in wolves and assumed to be the ancestral state.[7] The undercoat is absent in single-coated breeds which is assumed to be the derived state.[7]

Hair and feathers are produced from follicles. Follicles serve to generate, attach, and support hair or feather shafts. Further, hair follicles are categorized as simple and compound… horses and cattle only have simple follicles…, whereas **dogs and cats have both simple follicles interspersed with compound follicles (multiple hair shafts emerge from one infundibulum)**. Hair growth begins at the deepest portion of the follicle, the bulb; a specialized structure, the dermal papilla, induces growth of the hair follicle and hair production.

Hair follicles are classified as *primary or secondary,* and *simple or compound.* **Primary hairs** have a large diameter… **Secondary hair follicles** are smaller in diameter… Follicular arrangement in **dogs and cats consists of 2-5 large primary hairs surrounded by groups of smaller secondary hairs.** … All 3 layers of the inner root sheath keratinize… and become fully keratinized and disintegrate at the level of the isthmus. The inner root sheath is responsible for providing the rigid support for the developing **hair and its final shape, for instance, twisted hair follicles produce curly hairs.**

The page says that all mammals possess hair in some form, and that the term pelage refers to the entire hairy coat of a mammal without distinguishing between hair and fur. It also states that dogs commonly described as having hair or fur are both being described as having mammalian hair.

The cuticle of **Canis lupus familiaris hair** may be indistinct, but if one succeeds in observing it, among the special features it is worth emphasising the presence of imbricate type scales.[1] The diameter of the medulla in **dog hair** is usually 1/2, while the medulla in cat hair is thicker (over 1/2 the width).[1] It was shown that **dog’s hair** was longer than cat’s (M = 3.28; SD = 1.62 vs M = 2.93; SD = 1.28).[3]

The hair of **Canis lupus** can be identified with its unique medullary characteristics, i.e. the composition of medulla – ‘multicellular’, structure of medulla – ‘simple or narrow medulla lattice’ and the ‘circular or reniform’ shape cross-section.[4] Scale position, structure of scale margins and distance between scale margins are described for the **hair of Canis lupus**.[4]

The hairy skin of an adult dog contains **complex hair follicles that are bundles of hairs that share common openings on the surface**. The hair shaft consists of a central medulla; a thick cortex, which forms the bulk of the hair; and a single-layered cuticle on the outside. The keratin shaft of the hair is formed by the germinative epithelium of the bulb region, which is active only during the time of hair growth.

Hair follicles are formed by a downward invagination of the surface ectoderm and are essentially an infolding of the epidermis. Hair follicles are classified as primary or secondary and simple or compound. **Dogs, cats, rabbits, chinchillas, sheep, goats, camelids, and ferrets have compound hair follicles; this gives them their dense coats.** The pilosebaceous unit of a compound hair follicle is composed of one or more primary hair follicles surrounded by multiple secondary hair follicles.

Other important parts of the skin include **skin appendages (such as hair and claws)** and subcutaneous muscles and fat. Hair follicles, oil and sweat glands, and claws are skin appendages that grow out of the epidermis. **The hair follicles of dogs are compound, which means the follicles have a central hair surrounded by 3 to 15 smaller secondary hairs all exiting from one pore.** Dogs are born with simple **hair follicles** that develop into compound **hair follicles**.

The length of the **hair covering the body**, its hardness, and its texture vary depending on the level of selection of the breeds for their woolly abilities.[2] Dog (*Canis lupus familiaris; 2n = 78*) is a domestic animal that presents a great diversity of breeds which differ in morphology and also in the characteristics of their **hair** and coat.[2]

The coats of **domestic dogs** are of two varieties: "double" being common with dogs (as well as wolves) originating from colder climates, made up of a coarse guard **hair** and a soft down **hair**, or "single", with the topcoat only.[10] Coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth.[10]

Cross-species summary: **Long hair = angora**.[5] A mutation in the FGF5 gene had been shown to be causal of **hair length** by Housley and Venta (2006).[5] Genotyping of 218 dogs from three breeds fixed for **long hair**, eight breeds fixed for short hair and five breeds in which long hair is segregating provided evidence that the missense mutation is associated with the **hair-length differences among these breeds**.[5] Everts et al. (2026) investigated a mixed breed dog and several Tibetan Mastiffs with long **hair** and reported four additional FGF5 variants as likely causal variants.[5]

The dermis is composed of a network of connective tissue that also contains nerves, blood vessels, **hair follicles**, and sweat and oil glands. The basic unit of hair production is the **hair follicle (folliculus pili).** Each follicle has one guard hair and up to 15 secondary hairs emerging from the same follicle. The smaller underhairs provide most of the insulation and softness.

The fur is produced by millions of mini-organs called **hair follicles (HFs)** that invaginate from the epidermis into the subcutis. The secondary HFs produce the undercoat or wool hair and are neither associated with apocrine glands nor with an arrector pili muscle. Both primary HF types are associated all over the body with sebaceous glands and apocrine tubular glands, and both glands secrete into the infundibulum of the HF.

The **hair follicle unit** consists of the hair follicle itself, the sebaceous gland, sweat gland and an arrector pili muscle… Carnivores (**dogs, cats, etc.**) have **compound follicles**, which means that **hairs produced by multiple hair follicles exit from the same infundibulum at the skin surface.** Some of these **hairs** are large-diameter ‘primary’ **hair shafts** and the remainder are small ‘secondary’ undercoat **hairs**.

The article states that the terms fur and hair are clear and simple and can distinguish canine coats into two genetic categories. It adds that all pelage, or the hair, fur, or wool that covers any mammal, is made purely of keratin.

**Canis lupus familiaris hair** is an extract from Canis lupus familiaris hair used in allergy testing.[11] It is described as "an extract from Canis lupus familiaris **hair** used in allergy testing".[11]

They (hair follicles) are epidermal invaginations originating from a bud where the **hair is manufactured and grows from the dermal papilla**. In dogs, several hair follicles can emerge from the same infundibulum, from 2 to 15; **there are 100 to 600 hairs/cm².** The hair consists of a central part called the medulla… then the cortex which contains keratinised cells… and finally the outer cuticle made of flattened, adherent keratin cells arranged like tiles.

The anagen **hair follicle** consists of 8 concentric layers… and **hair shaft (comprised of the hair cuticle, the cortex, and the medulla).** … The telogen HF consists of 2 main parts: the infundibulum and the isthmus… Instead, the **club hair** is anchored by trichilemmal keratin, protruding into the ORS. The term "club hair" refers to a fully keratinized **hair shaft** that remains in the follicle during the telogen phase.

It says that scientifically speaking, hair and fur are the same on a molecular level, both made of keratin and growing from hair follicles. It concludes that all dogs technically have hair, and the distinction lies in how that hair behaves and how much maintenance it needs.

Every **hair in the dog coat grows from a hair follicle**, which has a cycle of growing, then dying to be replaced by another follicle. When the follicle dies, the hair is shed during the moulting process. This applies to the entire coat covering the dog’s body, which is composed of numerous hairs resulting in the dog’s fur.

Every **hair in the dog coat grows from a hair follicle**, which has a three phase cycle, as in most other mammals. Most dogs have a double coat, **each hair follicle containing 1–2 primary hairs and several secondary hairs.** The primary hairs are longer, thicker and stiffer, and called guard hairs or outer coat… secondary hairs (undercoat) are smaller and softer than the primary hair.

Your dog’s skin will contain the following skin appendages: **Hair follicles; nails; sebaceous glands…** Dogs have what is known as a **compound hair follicle** – this means that they produce multiple hairs with different functions. Each strand will grow central guard hair… in addition, the guard hair will be surrounded by three to fifteen shorter hairs which create the undercoat.

The page explains that hair and fur are the same thing chemically, both made of keratin, and says that both fur and hair are scientifically identical. It also states that dogs technically have hair.

It states that there is no difference between dog fur and dog hair, and that your dog's fur and hair follicles are made of keratin, the same protein that makes up human and dog nails. It adds that there is no physiologic difference between dog hair and fur.

DOG *Canis lupus familiaris* GUARD **HAIR** Length: 45–60 mm on mane (German shepherd), 35–40 mm (Labrador retriever), 29–70 mm on back, 30–64 mm on sides, 9–60 mm on underside (German shepherd, husky and Labrador retrievers).[8] UNDERFUR **Length**: 20–30 mm on Labrador retriever.[6] Diameter range and medullary index are given for this underfur **hair**.[6]

Your pet’s **coat is made up of thousands of hairs** that are continuously shed as a result of stress. However, they are replaced almost immediately with more **hair.** This constant turnover of **hairs** contributes to the health and appearance of the dog’s skin and coat.

The page says that hair and fur are made of exactly the same material, keratin, and that from a developmental standpoint there is no distinction between the follicles from which hair, fur, eyelashes, whiskers, wool, or porcupine quills grow. It concludes that scientifically, there is no distinction at all between hair and fur.

The article quotes a simple answer: 'There isn’t.' It states that hair and fur are the same thing.

Domestic dogs (*Canis lupus familiaris*) are derived from wolves and share similar coat structure, in which the term "**hair**" is used in scientific contexts to describe the individual filaments forming the coat.[10] In mammalogy and comparative biology, "fur" typically refers to the collective pelage, while "hair" refers to the anatomical keratinous strands; thus domestic dogs are described as having **hair** that forms their fur or coat.[7]

The page states that the coat of the domestic dog refers to the hair that covers its body. It also says that fur and hair are often used interchangeably when describing a dog's coat.

Fur typically refers to the thick, soft, and short **hair covering the body**, providing insulation and protection. On the other hand, hair refers to the longer, coarser strands found in specific areas like the tail and ears… Hair follicles in dogs go through a growth cycle consisting of three main phases: anagen (growth), catagen (transition), and telogen (resting).

The hair can be divided into two parts, the root and shaft. A pouch-like structure called follicle surrounds the hair root… The cells in the center of bulb divide; the newly divided hair cells push the previous cells up… forming hard hair shaft. This description applies generally to mammalian hair, including that making up a pet’s coat such as in dogs.