1. The prevalence of "backyard breeders."

The marketability of these breeds has made them very popular among breeders, who are now trying to breed them more than ever to benefit from the high price tag. Just to preface: not all of these breeders are bad. There are breeders who are reputable and maintain the health of and the best conditions for the dogs.

However, due to the popularity of the dog, there are many more "backyard breeders" who are just using the dogs to make money. The animals do not live in very good conditions and both the parents and the puppies have a greater risk of health issues.

In an article on the website "Terribly Terrier," Mat Jobe goes into further detail about some of the health risks animals can have from backyard breeders. Jobe says that, along with breeding dogs with their relatives, these breeders will sometimes starve the puppy to stunt their growth. Also, the dog mothers in these typically horrible conditions can suffer from more complications during birth. While some reputable breeders do exist, Jobe claims that many of these people do not wish to sell teacup puppies, so there are most likely more backyard breeders benefiting from this type of dog.

2. The large amount of health issues.

Since teacup breeders most likely consider and value the dogs' size over their health, the tiny puppies can have a wide variety of health problems. According to "petMD," these dogs are prone to seizures, heart defects, respiratory problems, and arthritis. Also, these puppies can suffer from chronic low blood sugar, which requires constant monitoring by the owner. Jobe's article states that, if their blood sugar is too low, the dogs can have seizures, or, in more extreme cases, die.

Many teacup dogs are also more likely than larger dogs to suffer from major injuries and bone fractures if they accidentally fall from a piece of furniture, are stepped on, or are dropped. This causes the owner to have to be much more cautious around their dog.