An autistic boy who cannot be physically touched or hugged by anyone has kindled an unlikely friendship with a new four-legged friend – Tornado the service dog.

Five-year-old Kainoa Niehaus travelled from Japan to the 4 Paws For Ability centre in Ohio, USA, after waiting for more than two years for a dog to become available.

It was love at first sight, and Kainoa’s mother was quick to post a photograph of her son lazily resting his head on Tornado the golden retriever.

“See this moment? I’ve never experienced a moment like this,” Shanna Niehaus wrote.

“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.

“This is the face of a mom 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.”

4 Paws For Ability is a charity organisation which provides dogs to disabled children and veterans who have lost the use of their limbs or hearing.

Ms Niehaus said: “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.”