Darla Reed and her dog, Galant, pay visits to dozens of patients at Rady Children's Hospital in San Diego, Calif. Reed and her dog are one of 33 canine volunteer teams for the program, which launched in 1990.
Spencer Kerr is undergoing chemotherapy for leukemia. The 14-year-old says a visit from Galant is powerful medicine.
"It's definitely the best part of the day is when a dog comes," Kerr told CBS News' Teri Okita. "They make me feel better."
In the past three decades, pet therapy programs have made significant advancements and have grown in popularity. Research has found that patients are happier, more alert, active and less anxious when a pooch pops by. Some studies have shown that cortisol levels, also known as the stress hormone, drop significantly when a hospital patient has contact with a dog.
The American Humane Association recently headed to Capitol Hill to request funding for animal-assisted therapies. In May, the organization launched a large-scale clinical trial to examine the benefits of canine-assisted therapy for pediatric cancer patients and their families. The research is funded by the Pfizer Foundation and Zoetis, a global animal health and medical company.
At Rady Children's Hospital, the canine volunteers make about 15,000 playroom and bedside visits each year. The program is so popular that the wait list to become a dog team volunteer is two years long.
Dogs involved in the program have to complete a physical, pass a monthly temperament test, a loud noise test, and a "pull" test to see how they'd react if a child pulls on their tail.
Reed has seen the benefits of the therapy herself. Her son, Grant, battled a brain tumor for years, but a visit from a dog always seemed to cheer him up. Grant had his own canine companion, Apache, who comforted him until he died. The experience inspired Reed to volunteer with Apache and then with Galant.
"When you walk into a room, and as you saw, every one of those kids -- and their parents, too -- got a big smile on their face," Reed told CBS News.