Though it's always a surprise, it's no longer novel to spot a pair of eyes peeking out of a shoulder bag.

Small breeds such as Yorkshire Terriers have boomed in popularity, according to purebred dog registries. Those don't even take into account other, ubiquitous mixes such as Yorkipoos (Yorkie-Poodle crosses) and Maltipoos (Maltese-Poodle crosses). And Chihuahuas are in such demand that the best place to adopt one is at a shelter! 

But small dogs require special care. The list of things that can go wrong with tiny dogs is a long one, and veterinarians see it all: from defective knees, hips and shoulders to heart and liver problems, collapsing cartilage in the neck, troublesome teeth, overall fragility and easily broken bones. Tiny dogs can also be hard to house-train since they have small bladders and need to go outside more often.

Some problems can be prevented through ethical breeding practices such as screening for genetic defects or with more careful handling to prevent injury, but many medical issues just come with being little (the most vulnerable of these dogs are the smallest of the small!).

Health problems don't stop the unscrupulous from breeding, but they should stop dog owners from buying. Pet lovers will do best by avoiding those who sell the tiniest of the tiny or any small dog before it is old enough. Reputable breeders usually won't let small-breed puppies go until they're 12 weeks old, since younger puppies can die if not fed every four hours. 

That doesn't mean they're not wonderful pets — they are! — but owning a small dog does mean you have to learn about their special needs to keep them healthy and happy.

This article was written by a Veterinarian.