Melissa Soto cuddles with a therapy dog near a memorial for the victims of the Pulse nightclub shooting in Orlando, Florida. The attack, which killed 49 people and injured 53, is the worst mass-shooting event in American history.<br /><br />Research shows that petting a dog can lower blood pressure, decrease anxiety and release oxytocin, a hormone associated with bonding and affection.
Melissa Soto cuddles with a therapy dog near a memorial for the victims of the Pulse nightclub shooting in Orlando, Florida. The attack, which killed 49 people and injured 53, is the worst mass-shooting event in American history.

Research shows that petting a dog can lower blood pressure, decrease anxiety and release oxytocin, a hormone associated with bonding and affection.
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Meet therapy dog Chilly Pasternak from Richmond, Virginia. Why are dogs used so often in therapy? Researchers point to the fact that dogs are the only non-primates that will look us in the eye. And brain scans show that dogs really do love us: Their brains light up in response to human smells, especially that of their owner.
Meet therapy dog Chilly Pasternak from Richmond, Virginia. Why are dogs used so often in therapy? Researchers point to the fact that dogs are the only non-primates that will look us in the eye. And brain scans show that dogs really do love us: Their brains light up in response to human smells, especially that of their owner.
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Fifteen-year-old Shayla Kline, left, pets Rex the therapy dog while getting a hug from her mother after a shooting in October 2014 at a high school in Marysville, Washington. Four students were killed, and one more was wounded. <br /><br />Why are dogs so good at comfort? Actually, not all are. A good therapy dog needs, above all, to have a great temperament. That means they should be calm at all times, even in the face of a hug that's too tight, loud noises and an occasional poke or two. They also need to love strangers as well as their own humans. And they need a well-trained human to be with them as part of the therapy team.
Fifteen-year-old Shayla Kline, left, pets Rex the therapy dog while getting a hug from her mother after a shooting in October 2014 at a high school in Marysville, Washington. Four students were killed, and one more was wounded.

Why are dogs so good at comfort? Actually, not all are. A good therapy dog needs, above all, to have a great temperament. That means they should be calm at all times, even in the face of a hug that's too tight, loud noises and an occasional poke or two. They also need to love strangers as well as their own humans. And they need a well-trained human to be with them as part of the therapy team.
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After the Boston Marathon bombing in April 2013, A.J. Feltner Harrison pets two certified therapy dogs, Archie, left, and Diva. The 13-year-old witnessed the initial shots fired when bomber Dzhokhar Tsarnaev was caught in Watertown, Massachusetts. The bombing, which occurred at the finish line of the marathon, killed three people and wounded at least 180.
After the Boston Marathon bombing in April 2013, A.J. Feltner Harrison pets two certified therapy dogs, Archie, left, and Diva. The 13-year-old witnessed the initial shots fired when bomber Dzhokhar Tsarnaev was caught in Watertown, Massachusetts. The bombing, which occurred at the finish line of the marathon, killed three people and wounded at least 180.
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A young boy pets a therapy dog named Toby inside Terminal 2 at San Francisco International Airport on December 3, 2013 in San Francisco, California. The San Francisco SPCA and San Francisco International Airport joined forces to launch a new program called "Wag Brigade" that will have a team of certified therapy dogs that will patrol the airport's to help calm stressed travelers during the busy holiday travel season.
A young boy pets a therapy dog named Toby inside Terminal 2 at San Francisco International Airport on December 3, 2013 in San Francisco, California. The San Francisco SPCA and San Francisco International Airport joined forces to launch a new program called "Wag Brigade" that will have a team of certified therapy dogs that will patrol the airport's to help calm stressed travelers during the busy holiday travel season.
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Patient Jesse Palado lets out a squeal as he's caught by surprise with a big wet kiss from Henry, a golden retriever, during a pet therapy visit from the dog in Palado's room at Cedars Sinai Hospital, Thursday morning in Los Angeles. The pet therapy program uses volunteers and their dogs to bring comfort and distraction to patients.
Patient Jesse Palado lets out a squeal as he's caught by surprise with a big wet kiss from Henry, a golden retriever, during a pet therapy visit from the dog in Palado's room at Cedars Sinai Hospital, Thursday morning in Los Angeles. The pet therapy program uses volunteers and their dogs to bring comfort and distraction to patients.
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Addison Strychalsky, 2, of Newtown, Connecticut, pets Libby, a golden retriever therapy dog, during a visit to a memorial for the Sandy Hook Elementary School shooting victims. Twenty children and six adults were shot to death in their elementary school on December 14, 2012, in Newtown. <br />After visits by therapy dogs, parents told stories of children speaking for the first time since the shootings and telling the dogs about what they had experienced.
Addison Strychalsky, 2, of Newtown, Connecticut, pets Libby, a golden retriever therapy dog, during a visit to a memorial for the Sandy Hook Elementary School shooting victims. Twenty children and six adults were shot to death in their elementary school on December 14, 2012, in Newtown.
After visits by therapy dogs, parents told stories of children speaking for the first time since the shootings and telling the dogs about what they had experienced.
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United Airlines employee, Lisa Alexander pets Rugi, a dog that was part of United Paws, an United Airlines program that allows passengers to interact with comfort dogs at Washington Dulles International Airport on Monday December 21, 2015 in Dulles, VA.
United Airlines employee, Lisa Alexander pets Rugi, a dog that was part of United Paws, an United Airlines program that allows passengers to interact with comfort dogs at Washington Dulles International Airport on Monday December 21, 2015 in Dulles, VA.
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A young boy pets Abby, a Golden Retriever, as Barnabas, stands at left at a memorial to the victims of the Sandy Hook School shooting in the center of Sandy Hook Monday, December 17, 2012 in Newtown, Connecticut. The dogs were among nine therapy dogs brought to Sandy Hook from Portage, Indiana, with the Holy Cross Lutheran Church to help mourners cope with the devastating loss. Seven of the dogs were brought to a private space where the Sandy Hook students were gathered to comfort them.
A young boy pets Abby, a Golden Retriever, as Barnabas, stands at left at a memorial to the victims of the Sandy Hook School shooting in the center of Sandy Hook Monday, December 17, 2012 in Newtown, Connecticut. The dogs were among nine therapy dogs brought to Sandy Hook from Portage, Indiana, with the Holy Cross Lutheran Church to help mourners cope with the devastating loss. Seven of the dogs were brought to a private space where the Sandy Hook students were gathered to comfort them.
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Frank Shane and his dog Nikie, the only therapy dog certified to work at the World Trade Center terrorist attacks site, overlook ground zero Friday, Jan. 18, 2002, in New York, while waiting to comfort workers undergoing the stress of working at the site.
Frank Shane and his dog Nikie, the only therapy dog certified to work at the World Trade Center terrorist attacks site, overlook ground zero Friday, Jan. 18, 2002, in New York, while waiting to comfort workers undergoing the stress of working at the site.
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