Chihuahua

Generally not with young children, and the reason is physical, not just temperamental. At 2-6 lb a Chihuahua can be seriously hurt or killed by being dropped, stepped on, or handled roughly, and a frightened small dog often responds by snapping. They can do well with older, gentle children who understand how to handle a fragile dog. For households with toddlers, a sturdier breed is the honest recommendation; if you already have both, supervise every interaction without exception.

Most Chihuahua aggression is fear-and-undertraining, not breed nastiness. Owners routinely tolerate guarding and snapping in a 4-lb dog they'd never allow in a 40-lb one, so the behavior is never corrected and the dog learns it works. It is largely preventable and improvable with early socialization, consistent training, and treating the dog like a dog rather than an accessory. Reward calm behavior, don't reinforce 'protective' snapping by coddling, and get a professional trainer if it's already established.

Chihuahuas are long-lived — typically 14-16 years, sometimes longer. The most common things that shorten that are largely owner-influenced: untreated dental disease (which is painful and stresses the heart), preventable physical injuries from falls and accidents, and heart valve disease in old age. Lifelong tooth brushing, hazard-proofing the home, keeping the dog lean, and routine vet checks for heart murmurs are what turn a 12-year Chihuahua into a 16-year one.

They need only about 20-30 minutes of walking plus indoor play a day, which makes them one of the better true apartment breeds. The apartment caveat is barking: Chihuahuas are alert and vocal, so without training they will alarm-bark at hallway noise and neighbors. Walk them on a harness rather than a collar to protect a delicate trachea, and don't skip walks just because the exercise need is small — they still need stimulation and socialization.

It's dangerously low blood sugar, a real risk in Chihuahua puppies and very small adults. A missed meal, stress, cold, or too much activity can cause wobbliness, glazed eyes, weakness, and progress to seizures or collapse within hours. It is an emergency: rub honey or corn syrup on the gums and get to a vet immediately. Prevent it by feeding small meals 3-4 times a day for puppies and at least twice daily for adults, and keep a sugar source on hand.

A breeder who health-tests should have a cardiac evaluation (for heart murmurs/valve disease), a patellar luxation evaluation, and an ophthalmologist eye exam on the breeding dogs, and should be candid about hydrocephalus history in the line. Ask to see certificates and meet the parents for temperament. A reputable breeder who health-tests or a breed rescue is far cheaper over a 15-year lifespan than an untested pet-store or backyard puppy whose knee or heart problems surface later.