A woman with dementia was punched in the face while she was wearing a badge saying "I have Alzheimer's please be patient".
Joy Watson, 61, has been left with a broken eye socket following the attack on Sunday in Bridlington, East Yorkshire.
Mrs Watson, of Eccles, Salford, said a man had attacked her after she told him he was mistreating his dog.
Humberside Police has confirmed it is investigating.
Mrs Watson, who was given a Points of Light award by former Prime Minister David Cameron for her volunteer work, was at a roadside cafe having breakfast at about 10:00 BST.
She complained to the man about his treatment of the animal and urged him to be more gentle but was told "it's none of your business".
Mrs Watson said she warned the man again when she saw him putting the dog on the seat of his car without a belt.
But the man swore at her and then punched her.
Mrs Watson, who was visiting Bridlington to watch some friends take part in a cycle race, said: "He gave me one massive hit - a huge thump to which I fell and hit my back on the concrete.
"He left me without knowing whether I was alive or not."
Police said the suspect was in his 60s and wearing fawn and brown coloured clothing.
A spokesman said: "The victim, who is in her 60s and from the Manchester area, saw what she reported as a man mistreating his dog.
"She confronted the individual who then allegedly assaulted her, leaving her with an eye and head injury which required hospital treatment."