Police are hunting the dog's owner after the 7.30am attack outside Safeway in Cherry St, Werribee.
The owner fled without helping Jean Manning, 72, who was bleeding from bites to her arm.
Ms Manning said her life flashed before her eyes when the dog rushed her as she stepped out of her car.
"It scared the living daylights out of me," she said.
"It was vicious and just ran at me totally unprovoked and sank its teeth into my arm."
Paramedics treated the bites before taking her to Werribee Mercy Hospital.
Sen-Constable Ely Reynolds, of Wyndham North Police, said it appeared the owner had tied the dog loosely to a trolley bay when he went inside the supermarket.
"On returning to the dog he failed to render any assistance or provide his details to the victim before fleeing the scene," Constable Reynolds said.
The attack follows the fatal mauling late last year of Ayen Chol, 4, killed in her St Albans home by a neighbour's pit bull mastiff.
"All dog owners have to be responsible for their animals and make sure they are properly restrained and controlled in a public place," Constable Reynolds said.
Police have released an image of the dog owner from CCTV footage. He is Caucasian, about 185cm and thin with a goatee beard. Anyone with information should call Crimestoppers on 1800 333 000.
(Sunday Herald Sun - Jan 14, 2012)
