A 12-year-old was bitten by a Staffordshire bull terrier that was on a lead walk last week.
The bite on the back of the boy’s left thigh punctured the skin. He was treated at the Milton Keynes walk-in centre.
Police are now searching for the dog walking who is in her mid-forties, with shoulder-length straight black hair. She was wearing black trousers and a black long sleeved T-shirt.
She was walking the dog in Benbow Crescent, Shenley Church End when the victim was hurt at around 8am on Thursday morning.
The dog is no taller than the victim’s knee and is brown in colour.
PC Stephen Coley said: “Clearly this will have been a distressing incident for the victim, and we are appealing to members of the public to please come forward if they have any information, by calling the 24-hour Thames Valley Police enquiry centre on 101.”