The researchers say that their spray has the potential to break up beta amyloid, a sticky protein that clogs up the brain in Alzheimer's patients to destroy connections between brain cells.
Stressing that phages are typically known to kill bacteria, the researchers claimed that they were the first to show that phages can affect plaques in the brain also.
They revealed that tests on mice had demonstrated that a regular treatment with the phages for a year cuts the amount of amyloid in the rodents' brains by 80 per cent. It also improved the mice's memory and learning, and restored their sense of smell that is often lost early in the onset of Alzheimer's.
"The mice showed a very nice recovery of their cognitive function," the Daily Mail quoted Professor Beka Solomon of Tel Aviv University as saying.
She revealed that once the amyloid plaques have broken up, the phages are naturally flushed out of the body without causing any side-effects.
"The phages are going into the brain, they do their work and then the body gets rid of them," she said.
As the drug is administered through the nose, it can sneak into the brain past the blood-brain barrier, a membrane that usually prevents drugs and other toxins from entering.
Professor Solomon's study has been hailed by British scientists, but with a warning that it may take many years before the treatment becomes saleable.
"Penetrating the bloodbrain barrier is a very real and current challenge for researchers looking at new treatments for Alzheimer's disease and other forms of dementia. We need to be especially cautious as previous treatments using phages for other types of conditions have resulted in side-effects," Susan Sorensen of the Alzheimer's Society said.
"We are a long way from this novel way of administrating treatment being translated into practice," she added.