For the owners of some breeds it seems almost a point of pride to claim that their dogs are covered in hair, rather than fur. The belief is that this accounts for why people may be less allergic to some breeds. What interested me was not that there was a difference in allergic reactivity, but in the distinction between hair and fur. It doesn't take much analysis to see that the ordinary distinctions between fur and hair do little to explain the difference in allergic reaction.

When these breed owners are asked about the difference between hair and fur the most common definition is that fur stops growing after a certain length while hair keeps growing. Some will go so far as to suggest that the hair will grow literally forever if it is not artificially shortened by cutting, breakage or other damage.

I love it when I hear that explanation. Are your arms covered with hair? or fur? Your underarms have fur? or hair? and well do you consider yourself to be furry down below? If you accept the definition that the distinction between hair and fur is that hair continues to grow unless cut, then you are furry on your arms, legs, eye lashes, eye brows, underarms and ... down there. According to that definition the only hair on your body is on your head and face, and everything else is fur.

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Poodles have eye lashes. Are the eye lashes cut to prevent them from growing forever? Or do they have a natural length and stop growing on their own? If you accept the distinction some offer between fur and hair then you'd have to say that the eye lashes are made of fur while the dog's body is covered in hair. This just isn't consistent with the ordinary definition of fur.

And another small note to ponder - are wool sheep that must be shorn covered in hair? or fur? In sheep the "hair sheep" are the ones that don't require sheering.

The ordinary definition of fur is related to the density of the hair, and sometimes its softness, rather than growth pattern. This is more consistent of the biology involved, but fails in distinguishing the poodle coat as "hair" vs the Doberman coat as "fur". Logically the terms "hair" and "fur" are not good descriptors of the differences between the coats of these two breeds.

Let's take a closer look at the biology of hair.

Each strand of hair grows from the root. Each strand of hair goes through a cycle of growing or not growing. The cycles vary from person to person. Only the part under the skin grows. Cutting the hair does not affect the hair follicle. Uncut hair grows at the same rate as cut hair. Hair growth is affected only if the hair follicle is affected.

In mammals hair grows in cycles. Anagen is a period of new hair growth. The longer the anagen period, the longer the hair grows. Human scalp hair may stay in anagen for 2-6 years. Human hair on arms and legs may stay in anagen for only 30-45 days. Catagen is a transition phase. During catagen growth stops and the outer root sheath shrinks attaching to the root of the hair. Telogen is the resting phase. For human scalp hair the resting phase is about 100 days. The telogen phase for human hair on arms and legs is much longer than for scalp hair. Exogen is when the hair falls out, and the follicle enters a new anagen period, growing a new strand of hair.

In dogs, as in all other mammals, some hair follicles are in anagen, some in catagen, some in telogen. Shedding, length of hair and presence or absence of an undercoat depend upon the timing of these cycles and the ratio of hair follicles in the various stages. Differences between summer coat and winter occur because during the summer a greater number of follicles remain inactive. Some breeds, e.g. poodles, tend to be low shedding because almost all of their follicles are in anagen (growth cycle) almost all the time; their hair continues to grow and has to be clipped. Some breeds of dog, e.g. Chinese Crested have most of their follicles in telogen and, thus, may be almost completely hairless. Both breeds are often listed as recommended for allergy sufferers.

I liked this humorous definition from LususNaturae

Dogs and cats: If it's where it belongs (on the animal), it's
fur; if it's where it doesn't belong (on your black slacks), it's hair.

Humans: If it's where it belongs (on the top of your head),
it's hair; if it's where it doesn't belong (on your back), it's fur.

The bottom line is that hair doesn't grow forever. It grows as long as the hair follicle is in active growth. How long a particular hair follicle is in active growth depends upon various factors. It could be genetically programmed to be in active growth for years, or only for weeks. Most dog breeds have a coat that is genetically programmed for a shorter growth cycle than those similar to the poodle coat. The coats of dogs with a long hair growth cycle will shed less.

The poodle coat, and the coats of other breeds frequently recommended to the allergic, have another quality beyond the long growth period. These coats tend to be both tightly curled, and usually lacking in undercoat. This combination tends to keep dead hair from detaching and floating in the air, and it tends to retain the dander, which is the most common source of allergens. Typically in these curly coated breeds the dead hair must be manually removed by grooming or it will stay tangled in the coat causing matting.

Another source of allergic reactivity is the pet saliva. The grooming requirements for these breeds also encourage more frequent bathing, which further reduced allergens. The coats also tend to be somewhat less coated in the water resistent oils common in many sporting breeds. The most likely reason some coated breeds cause less allergic response is problaby related to lower shedding and more frequent grooming and bathing.

Yes, poodles are coated in hair. So are most other dog breeds. All hair, including poodle hair, has a natural length. The term "hair" is not properly restricted only to that which has a long period of growth. Fur is a reasonable description for the plusness of a coat, it is not a reasonable description for hair that merely has a short growth period.

Allergic to Dogs?
http://sweet-lucys.com/allergictodogs.html

ASK THE EXPERTS: BIOLOGY: What is the difference between hair and fur?
http://www.sciam.com/askexpert_question.cfm?articleID=0006E5B1-64B0-1C72-9EB7809EC588F2D7&catID=3

Foster & Smith, Pet Eduction: Skin & Hair Anatomy & Function
http://www.peteducation.com/article.cfm?cls=2&cat=1581&articleid=357

Mayo Clinic - Pet Allergies, When You Can't Dodge the Dander
http://www.mayoclinic.com/health/pet-allergies/HQ01204

Sneeze-Free Dog Breeds: Allergy Management & Breed Selection For The Allergic Dog Lover by Diane Morgan

Allergic To Pets? The Breakthrough Guide To Living With The Animals You Love by Shirlee Kalstone

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