A dog of any breed has the potential to be reactive. Genetics do play a role, so you may see increased reactivity in high-energy breeds like German shepherds, border collies, chihuahuas, and more. However, a dog isn't guaranteed to be reactive just because they're from a specific breed. Poor socialization in puppyhood, traumatic experiences, and lack of training can all contribute to reactivity.A dog of any breed has the potential to be reactive. Genetics do play a role, so you may see increased reactivity in high-energy breeds like German shepherds, border collies, chihuahuas, and more. However, a dog isn't guaranteed to be reactive just because they're from a specific breed. Poor socialization in puppyhood, traumatic experiences, and lack of training can all contribute to reactivity.