Kainoa Niehaus, who finds it painful to be touched or hugged, finally met canine Tornado in Ohio having been on a waiting list for two years. His family are Americans who live in Japan.

Non-profit organisation 4 Paws For Ability, who aim to enrich the lives of children with disabilities by placing them with task-trained service dogs, shared the ‘truly magic’ moment on Facebook.

The five-year-old boy’s mother Shannon, who cried tears of happiness when the pair met, explained she had “never experienced a moment like it”.

“This picture captures the face of a mother who saw her child, who she can't hug, wash, dress, snuggle and touch freely lay on his new service dog of his own free will, with a purposeful, unspoken attachment,” she explained.

“This is the face of a mum who has seen her son experience countless failed social interactions on the playground in an attempt to have a friend. Any friend. Any kind of connection.

“She has sat with her son while he has cried at night for months because he has no consistent connections outside of the family no matter how hard he tries and no matter what he works hard on in his autism therapies.

"It doesn't transfer to the natural occurring world for him. And now she is sitting behind her son silently watching this moment, with the air sucked from her lungs, and no words to say.”

She added: “It's worth every fight for services for my son, every diagnosis, every new provider, every dollar spent, every paper filled out, every school meeting, every shed tear, every step forward, every step back, and every wonder of the unknown future. Somehow because of this - because of Tornado - I know everything will be okay.

“As a mother, I have seen countless challenging and painful moments my son has encountered and cried countless more. Yesterday however, I cried for a different reason. It is a feeling that is indescribable.”

Earlier this year, this smiling dog almost lost his new home after an adoption selfie alerted police.

While these loyal dogs also won internet praise after refusing to leave side of dying baby girl at hospital.