Kyle McSkimming was rushed to hospital after he was attacked by the shar-pei dog, called Hulk.
The boy had been visiting his brother's house in Kettering, Northamptonshire, when the family pet clamped its jaws around Kyle's face when he went to put a bandana on the dog's back.
His brother's girlfriend battled to free the boy before calling the emergency services.
Kyle was then taken to hospital where he underwent a three hour operation to treat two large cuts under his eye and mouth.
He required 33 stitches - nine under his eye, six on his lip and 18 inside his mouth. Doctors have warned Kyle he may now be scarred for life.
The dog, which belonged to Kyle's brother Blayne Prickett, 20, has since been destroyed.
Horrified mother Kerrie Sweeney, 32, said: 'His brother had gone out to the shop and Kyle was leaning over to put a bandana on the dog and it just went for him. They had only recently got the dog from another family in the town and it turns out he had a bit of a history of being angry.
'Kyle's father Kevin called me up and told me Kyle had been bitten by a dog. I just thought it was a small scratch and maybe he needed a tetanus jab.
'When I arrived at the house there were police and ambulances there and my stomach turned. It was just awful - I was so scared. It could have killed him.
'Kyle's brother is devastated about what happened and was in shock at the time. Kyle is back at school now, he's still shaken by the whole incident but he's almost back to normal.
'The policeman told me afterwards that if they hadn't shot the dog it could have killed one of them - it was that vicious. It's been quite a harrowing ordeal.'
Kyle, who lives with his mum and her boyfriend Steffan Stokes, 32, in Barton Seagrave, Northamptonshire, said he was trying to keep the dog away from his young nephew when it turned on him.
He said: 'I was round my brother's house playing with the dog and my baby nephew. Hulk sat down and I put a bandana on his back.
'He then sort of went towards my nephew and I pushed his head away - and then he just went for me. It didn't seem to hurt much at the time - but I was just in shock at what happened.
'I had met Hulk before and he had always been a nice dog to me, but I think they are an angry type of dog. It was very scary.'
(Daily Mail - April 20, 2013)
