Yorkshire Terriers are very playful and energetic dogs. Many people who have a Yorkie as a pet have two, because they often have separation anxiety when left alone and 'they don’t enjoy being alone.' . 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'.