April 1, 2008 -- On Matthew Plunk's third birthday, his parents, Jeff and Jennifer, received some life-changing news: Their son had autism.
The diagnosis came as no surprise to the Plunks, who had long struggled to contain their son's emotional outbursts and antisocial behaviors.
"He had a lot of fears," said Jennifer. "Just a truck going by would make him want to climb up you."
After years of trying different therapies and experimental diets for Matthew, the Plunks noticed he had made significant progress but still suffered from intense anxiety and difficulty interacting with strangers.
"The biggest thing I was looking for [was] a calmness for Matthew," said Jennifer. "His mind is just going 90 miles an hour. It's like his foot is always on the gas pedal."
So when Matthew was 6, Jennifer went online in search of something else she hoped could help him -- a dog. She had heard about service dogs specially trained to work with children with autism so she researched a program that would help her find a canine companion for Matthew.
"I really believed in the calming impact that a dog can have," said Jennifer.
Her research led her to 4 Paws for Ability, one of several organizations that trains and places dogs to work specifically with autistic children, helping them to become calmer, more social and more comfortable in the world.
As part of their application to the training program, the Plunks submitted hours of home video to demonstrate the problems that Matthew was having, as well as lengthy descriptions of their family's habits and challenges.
Once accepted into the program, they were then required to raise the $12,000 necessary to train the dog, which they did through the generosity of friends, family and their community.
With the money raised, the Plunks headed to the 4 Paws center for a two-week training course in which they were introduced to Matthew's new service dog, Ajax, a Great Pyrenees-boxer mix.
"It was amazing," said Jennifer, describing their first day at the center. Matthew, who had always struggled with forming new bonds with strangers, recognized a picture of Ajax and immediately ran to him.
"It was very sweet," Jennifer said. "The first day of training, he said several times 'I love you, Ajax.' It was hard not to cry."
One year later, Matthew quickly calls Ajax his best friend and can barely be separated from his dog. He is noticeably calmer and more responsive, more attentive and focused on his schoolwork and he happily interacts with strangers in public -- typically to answer questions about Ajax.
"I can see a difference in him," said Jennifer. "Matthew is calmer. He enjoys having Ajax around."
Matthew's father, Jeff, agrees. "He really had a hard time even sitting still, and now he's much more calm."
Since Ajax's arrival, Matthew is also more confident and less prone to meltdowns, the intense and often inexplicable emotional outbursts that often go hand in hand with autism.
The Plunks are just one of many families ABC News spoke to that have had a profoundly positive experience by bringing an autism assistance dog into their home. As word spreads, hundreds of American families are now seeking the benefits of service dogs for their autistic kids.
Dionne Silvester was at a loss for what to do for Hunter, her 6-year-old autistic son who would not only climb the walls in their home, but consistently run away and disappear from his parents.
After a few terrifying experiences in which they thought they had genuinely lost their son, the Silvesters applied to 4 Paws to get a dog that would be able to "track" Hunter, or follow his scent if he went missing.
As part of last week's 4 Paws training session in Ohio, the Silvesters and 10 other families practiced tracking with their new dogs and were thrilled at the results.
"Now I can shop, where before, this would never happen, ever," said Wendy Gaines, one of the mothers at the session.
Like so many families, Gaines and the Silvesters had abandoned the idea of being able to take a simple trip to the store ? everyday tasks like this become almost unthinkable for families with autistic children because of their kids' unpredictable and hyperactive behavior while out in public.
While some children, including Matthew Plunk, can take anywhere from six months to a year to fully bond with their dogs, for other families the change is practically immediate.
"It was just like in an instant," said Bonnie Chachkes, a New York City mother of four. Her family got their dog, Lola, from the Northstar Foundation, another organization that works to train autism assistance dogs and place them with families.
Chachkes cannot imagine life without Lola, a dog being trained to accompany Chachkes daughter Deena, an overwhelmingly energetic 8-year-old who bounces off the walls and asks a nonstop flow of questions.
"This is her best friend," said Chachkes, watching the two play together. The changes Lola has brought about for Deena have been significant.
While it used to be nearly impossible for her to interact with other people in public, with Lola at her side Deena is noticeably calmer and can channel her energy into engaging in conversations about her dog.
In addition, Deena, who never slept because she bounced around uncontrollably and fidgeted all night long, can now sleep through the night because Lola lies on top of her in bed to keep her calm.
When asked how Lola has changed their lives, a huge smile crosses Chachkes' face.
"She's happy," she said, watching Deena feed Lola treats. "What could a mother ever want from her child?"
Trainers caution that autism assistance dogs may not be the right fit for every autistic child and that the dogs are not a cure-all. While the evidence at this stage is primarily anecdotal, researchers are working to create studies that will produce more scientific evidence supporting this therapy.
Of at least a dozen families interviewed for this story by ABC News, not one had a single negative comment about the program. On the contrary, families with the dogs were eager to spread the word to other parents with autistic kids, though they caution that the process is not a free ride.
"It's a journey," said Jennifer. "You've got to be willing to get in there and get your hands dirty, but it's definitely amazing. I would recommend it to anybody."
For more information on autism assistance dogs, check out the following organizations: