One of the most important aspects of owning a dog of any breed and of any size is to socialize him with all shapes, sizes, and kinds of people, as well as with other dogs. Without strong socialization skills, the Chihuahua can become distrustful of people and dogs and can become quite protective of its owner, not even allowing family members to be near that person. With practice and a bit of persistence, however, you can prevent or help your Chihuahua overcome being fearful or aggressive toward people and dogs.