Veterans interact with Alaskan Malamute sled dogs during the Phoenix Winter Games in Catterick Garrison in Richmond, England, on March 4, 2019. Kennels from the Alaskan Malamute Working Association have been providing sporting fun and excitement to injured service personnel and veterans as part of the Phoenix Winter Games at the Phoenix House Personnel Recovery Center, in Catterick. #

Atila, a trained therapeutic greyhound used to treat patients with mental-health issues and learning difficulties, falls asleep while being caressed by patients at the Benito Menni health facility in Elizondo, Spain, on February 13, 2017. The facility, based in a town near the border with France, uses the dogs to help patients develop social skills and a sense of autonomy. Alongside misty views of green, rolling mountains, petting sessions with the eight-month-old puppies have a calming effect, serving as an emotional outlet for patients who struggle to connect with others. #

David Villanueva, 44, poses with Argi, a trained therapeutic greyhound at the Benito Menni health facility in Elizondo, Spain, on February 13, 2017. When asked what the greyhounds meant to him, he answered: "Care." #

The therapy dog Perry plays with his owner and trainer, Isabel Garcia, after a workday helping calm autistic children during their dental appointments at Los Andes University Medical Center on the outskirts of Santiago, Chile, on April 28, 2017. #

The therapy dog Perry sits between the feet of a young autistic patient during his dental appointment at the Los Andes University Medical Center on April 28, 2017. Therapy dogs are trained to resist the noise from the dentist's drill, staying still in children's laps while they pull their hair and ears. #

Jacob Burns, an Army veteran, simulates having a panic attack as he works with Jersey, his new support dog, as part of a training session together on October 5, 2017, in Collinsville, Illinois. The nonprofit Got Your Six Support Dogs provides the specially trained service dogs at no charge to veterans like Burns, who suffers from post-traumatic stress disorder. After spending about a week getting to know each other, Burns will return home with his new companion to help combat the issues associated with PTSD. #

A therapy dog named Toby reacts as a traveler pets him inside Terminal 2 at San Francisco International Airport on December 3, 2013. The San Francisco SPCA and San Francisco International Airport joined forces to launch a new program called "Wag Brigade," a team of certified therapy dogs, set to patrol the airport to help calm stressed travelers during the busy holiday-travel season. #

The Children's Hospital patient Draegan Crabb, 9, of Dale, Oklahoma, pets a therapy dog as he listens to an announcement that The Children's Hospital at OU Medicine will be getting another therapy dog to add to their team of three dogs during a news conference on July 22, 2019, in Oklahoma City. #

Zucca, a Labrador retriever therapy dog, accompanies a child during a children dentist's session in a public hospital as part of a program to calm the fears of children in the dentist chair in Santiago, Chile, on May 8, 2018. #

Diego Rosales, who has autism, rests his hands on the paws of the therapy dog Zucca during his dental appointment at Los Andes University Medical Center on the outskirts of Santiago, Chile, on April 28, 2017. #

Aelane Vasquez, 9, reads with Leslie Hight, a therapy-dog handler for New York Therapy Animals, and Izzy, a reading-education-assistance dog, at Public School 57 in the Spanish Harlem section of New York City, on May 16, 2016. #

Elizangela Santos, a 35-year-old receiving cancer treatment, rubs the chin of a schnauzer dog named Paola in her bed at the Support Hospital of Brasilia, Brazil, on November 17, 2016. Once a week, patients receive visits from a special breed of therapists: dogs trained to help them in their recovery from disease or injury. #

Ann Davidson, a medical assistant from Canine Therapy Corps, speaks as a medical-center employee pets Rocco at Rush University Medical Center in Chicago on February 18, 2016. The medical center has offered monthly sessions of animal therapy for more than a year as an employee health and satisfaction program, using dogs from a local shelter and an animal-therapy group. #

A child pets a therapy dog at a facility for children in Bucharest, Romania, on February 17, 2017. An association for therapy dogs had organized a therapy session for children with Down syndrome. #

A rescue worker pets a therapy dog at the Oso fire station before a moment of silence for those lost in a mudslide exactly one week before, in Oso, Washington, on March 29, 2014. #

Lily Sroboda, 11, a patient at Childrens Hospital Colorado, gets a visit from Brownie, a therapy dog in the hospital's Prescription Pet Program, in Aurora, Colorado, on April 14, 2013. #

Paola laughs as Lancelot, an American cocker spaniel, walks on her bed at the SOLCA hospital in Quito, Ecuador, on July 25, 2012. The dog's owner said her dogs come to cheer up the most discouraged of the patients every Wednesday. #