1859

Florence Nightingale, widely regarded as the founder of modern nursing, made one of the earliest recorded observations of the emotional and psychological benefits of companion animals in healthcare settings.

While working in British military hospitals during the Crimean War and later writing about patient care, Nightingale noted that small pets—particularly dogs and birds—had a calming effect on psychiatric patients and the wounded. She observed that patients who were withdrawn, anxious, or severely ill often showed noticeable improvements in mood and responsiveness when allowed to interact with or care for an animal.

In her influential 1859 work, Notes on Nursing: What It Is and What It Is Not, Nightingale wrote:

“A small pet is often an excellent companion for the sick, for the long chronic cases especially.”

This simple statement reflected a profound insight: animals could provide comfort and companionship in ways that human caretakers sometimes could not. In the rigid, clinical settings of 19th-century hospitals, where mental illness was poorly understood and compassion was not always a given, the presence of an animal could ease suffering and bring a sense of normalcy.

While she didn’t use the modern language of “therapy” or “animal-assisted intervention,” Nightingale’s recognition of animals as a source of emotional support and healing paved the way for the more structured use of animals in mental and physical healthcare more than a century later.

Today, her observations are often cited as one of the earliest acknowledgments of the human–animal bond in medical care—a bond that would evolve into the formalized use of therapy dogs and other service animals in hospitals, rehabilitation centers, and beyond.

1914–1918 :

During the chaos of World War I, help didn’t always arrive on two legs. Sometimes, it came quietly—on four paws.

Mercy dogs, also known as Red Cross dogs or casualty dogs, were trained by military forces across Europe to do something extraordinary: save lives. These dogs didn’t carry weapons or attack the enemy. Instead, they wore saddlebags filled with bandages, water, and medical supplies, and ventured out onto the battlefield—often at night—to find wounded soldiers who had been left behind.

Trained to ignore the dead and locate the living, the dogs moved silently through the mud and wreckage, sniffing for signs of life. When they found a wounded soldier, they offered comfort and access to the supplies strapped to their sides. If the soldier was too injured to treat himself, the dog would return to its handler carrying a piece of the man’s uniform or gear, a signal that someone needed urgent help.

In one real-life account, a mercy dog crossed the battlefield under fire, locating a young soldier half-buried in earth and too weak to call for help. The dog lay beside him through the night, offering warmth and presence until medics could arrive. Stories like this were common—and lifesaving.

During World War I, Germany trained over 6,000 of these dogs, while France, Britain, and later the United States also built programs to support battlefield medical care using dogs. It's estimated that they helped save tens of thousands of lives. In addition to finding the wounded, some dogs even helped pull small carts or assisted medics in locating soldiers in areas too dangerous or remote for humans to reach.

Many did not survive. Those who did were often deeply affected by the horrors they witnessed—what we now recognize as trauma. But to the soldiers they helped, these dogs were more than tools of war; they were trusted companions and quiet heroes.

Although mercy dogs were used again in World War II and the Korean War, the programs eventually faded. Yet their legacy lives on in the roles of modern search-and-rescue dogs, medical alert dogs, and therapy animals. Their work laid the foundation for the service dog partnerships we rely on today—reminders that courage, compassion, and service can come from the most unexpected places.

1920s–1940s:

1920s–30s:

Sigmund Freud uses his dog, Jofi, during some therapy sessions, observing its calming influence on patients.

WWII (1939–1945):

Dogs continue to serve in military roles, offering comfort to injured soldiers and aiding medics.

1944:

"Smoky," a Yorkshire Terrier, is found in a foxhole in New Guinea and becomes the first documented therapy dog.

She comforts wounded soldiers in hospitals and is credited with improving morale and aiding recovery. Her work with Corporal William Wynne marks the first recorded use of a dog in a therapeutic hospital setting.

1960s–1970s:

1961:

Dr. Boris Levinson, a child psychologist, coins the term “pet therapy” after observing positive responses from a patient interacting with his dog, Jingles.

1976:

Elaine Smith, a nurse in New Jersey, founds Therapy Dogs International (TDI). The first organization dedicated to training and certifying therapy dogs.

1977:

Delta Society (now Pet Partners) is established, promoting research and training in animal-assisted therapy (AAT).

2020s–Present:

During the COVID-19 pandemic, therapy dogs are used to support healthcare workers and isolated individuals.

Scientific research continues to validate the emotional and physiological benefits of animal-assisted interventions.

Therapy dog teams become integral to mental health programs, veterans’ services, educational outreach, and crisis response.