The Yorkshire Terrier also known as "Yorkie" is a small dog breed of terrier type, developed in the 19th century in the county of Yorkshire, England to catch rats in clothing mills. The defining features of the breed are its size, 3 pounds (1.4 kg) to 7 pounds (3.2 kg), and its silky blue and tan coat. The breed is nicknamed Yorkie and is placed in the Toy Terrier section of the Terrier Group by the Fédération Cynologique Internationale and in the Toy Group or Companion Group by other kennel clubs, although all agree that the breed is a terrier. A popular companion dog, the Yorkshire Terrier has also been part of the development of other breeds, such as the Australian Silky Terrier.
For adult Yorkshire Terriers, importance is placed on coat colour, quality, and texture. The hair must be glossy, fine, straight, and silky. Traditionally the coat is grown-out long and is parted down the middle of the back, but "must never impede movement."
From the back of the neck to the base of the tail, the coat should be a dark gray to a steel-blue, and the hair on the tail should be a darker blue. On the head, high chest, and legs, the hair should be a bright, rich tan, darker at the roots than in the middle, that shades into a lighter tan at the tips. Also, in adult dogs, there should be no dark hairs intermingled with any of the tan coloured fur.
A newborn Yorkshire terrier puppy is born black with tan points on the muzzle, above the eyes, around the legs and feet and toes, the inside of the ears, and the underside of the tail. Occasionally Yorkies are born with a white "star" on the chest or on one or more toes. It is also common to find white patch on one or more nails. These markings fade with age, and are usually gone within a few months.
The typical fine, straight, and silky Yorkshire Terrier coat has also been listed by many popular dog information websites as being hypoallergenic. In comparison with many other breeds, Yorkies do not shed to the same degree, only losing small amounts when bathed or brushed. All dogs shed, and it is the dog's dander and saliva that trigger most allergic reactions. Allergists do recognize that at times a particular allergy patient will be able to tolerate a particular dog, but they agree that "the luck of the few with their pets cannot be stretched to fit all allergic people and entire breeds of dogs." The Yorkshire Terrier coat is said to fall out only when brushed or broken, or just said to not shed. Although neither of those statements agree with what biologists, veterinarians, and allergists know about dog fur, allergists "think there really are differences in protein production between dogs that may help one patient and not another", meaning that some allergic people may not have allergic reactions to a specific dog, like the Yorkie.
The ideal Yorkshire Terrier character or "personality" is described with a "carriage very upright" and "conveying an important air." Though small, the Yorkshire Terrier is active, loves attention, very overprotective and should not show the soft temperament seen in lap dogs. Yorkshire Terriers, also known as Yorkies, are a little harder to train than some other breeds of dogs. This results from their own nature to work without human assistance.
Yorkshire terriers tend to bark a lot. This makes them excellent watch dogs because they will sound the alarm when anyone gets near. This barking problem can be resolved with proper training.
The Yorkshire Terrier originated in Yorkshire (and the adjoining Lancashire), a rugged region in northern England. In the mid-19th century, workers from Scotland came to Yorkshire in search of work and brought with them several different varieties of small terriers. Breeding of the Yorkshire Terrier was "principally accomplished by the people—mostly operatives in cotton and woolen mills—in the counties of Yorkshire and Lancashire." Details are scarce. Mrs. A. Foster is quoted as saying in 1886, "If we consider that the mill operatives who originated the breed...were nearly all ignorant men, unaccustomed to imparting information for public use, we may see some reason why reliable facts have not been easily attained."
What is known is that the breed sprang from three different dogs, a male named Old Crab and a female named Kitty, and another female whose name is not known. The Paisley Terrier, a smaller version of the Skye Terrier that was bred for a beautiful long silky coat, also figured into the early dogs. Some authorities believed that the Maltese was used as well. "They were all originally bred from Scotch terriers (note: meaning dogs from Scotland, not today's Scottish Terrier) and shown as such...the name Yorkshire Terrier was given to them on account of their being improved so much in Yorkshire." Yorkshire Terriers were shown in a dog show category (class) at the time called "Rough and Broken-coated, Broken-haired Scotch and Yorkshire Terriers". Hugh Dalziel, writing in 1878, says that "the classification of these dogs at shows and in the Kennel Club Stud Book is confusing and absurd" in lumping together these different types.
In the early days of the breed, "almost anything in the shape of a Terrier having a long coat with blue on the body and fawn or silver coloured head and legs, with tail docked and ears trimmed, was received and admired as a Yorkshire Terrier". But in the late 1860s, a popular Paisley type Yorkshire Terrier show dog named Huddersfield Ben, owned by a woman living in Yorkshire, Mary Ann Foster, was seen at dog shows throughout Great Britain, and defined the breed type for the Yorkshire Terrier.
Health issues often seen in the Yorkshire Terrier include bronchitis, lymphangiectasia, portosystemic shunt, cataracts, and keratitis sicca. Additionally, Yorkies often have a delicate digestive system, with vomiting or diarrhea resulting from consumption of foods outside of a regular diet.  The relatively small size of the Yorkshire Terrier means that it usually has a poor tolerance for anesthesia. Additionally, a toy dog such as the Yorkie is more likely to be injured by falls, other dogs and owner clumsiness.  Injection reactions (inflammation or hair loss at the site of an injection) can occur. In addition they may have skin allergies.
The life span of a healthy Yorkie is 12-15 years. Under-sized Yorkies (3 pounds or less) generally have a shorter life span, as they are especially prone to health problems such as chronic diarrhea and vomiting; are even more sensitive to anesthesia; and are more easily injured.
Low blood sugar in puppies, or transient juvenile hypoglycemia, is caused by fasting (too much time between meals). In rare cases hypoglycemia may continue to be a problem in mature, usually very small, Yorkies. It is often seen in Yorkie puppies at 5 to 16 weeks of age. Very tiny Yorkie puppies are especially predisposed to hypoglycemia because a lack of muscle mass makes it difficult to store glucose and regulate blood sugar. Factors such as stress, fatigue, a cold environment, poor nutrition, and a change in diet or feeding schedule may bring on hypoglycemia. Low blood sugar can also be the result of a bacterial infection, parasite, or Porto systemic liver shunt. Hypoglycemia causes the puppy to become drowsy, listless (glassy-eyed), shaky and uncoordinated, since the brain relies on sugar to function.
Additionally, a hypoglycemic Yorkie may have a lower than normal body temperature and, in extreme cases, may have a seizure or go into a coma. It is always easier to prevent hypoglycemia than threat it. Preventing hypoglycemia requires you to keep your puppy out of stress, feed your puppy when it should be fed & give your puppy nutri-cal or ener-cal every day 2 or 3 times a day. A dog showing symptoms should be treated by a veterinarian immediately, as prolonged or recurring attacks of hypoglycemia can permanently damage the dog’s brain. In severe cases it can be fatal.
Traditionally, the Yorkshire Terrier's tail is docked to a medium length. Opposition to this practice began very early in the history of the breed; Hugh Dalziel, writing about Yorkshire Terriers in 1878, declared that "There is no reason for mutilating pet dogs, and perfect ears and tails should be bred, not clipped into shape with scissors." Often, a Yorkshire Terrier's dewclaws, if any, are removed in the first few days of life, another controversial practice.