Service dogs are often identified by wearing a service dog vest or tag, letting the public know that it is a service dog; otherwise, their handlers will find themselves having to explain everywhere that they go that their dog is a service dog. Some businesses, such as airlines, prefer to see an identification card or vest that indicates that the dog is a service dog.
The Americans with Disabilities Act has a specific definition of a disability, and it states essentially that a disability is a physical or mental impairment that substantially limits one or more major life activities of such individual.