People who come down with cold sores could develop a far more serious condition down the road – Alzheimer’s disease.

Researchers at the University of Manchester in England found the herpes virus behind cold sores is a major cause of the protein plaques that build up in the brains of people with Alzheimer's, the BBC reported.

The research team, led by Professor Ruth Itzhaki, found DNA evidence of the herpes simplex virus (HSV) type 1 in 90 percent of plaques in Alzheimer's patients' brains, according to the report.

"We suggest that HSV1 enters the brain in the elderly as their immune systems decline and then establishes a dormant infection from which it is repeatedly activated by events such as stress, immunosuppression, and various infections,” Itzhaki told the BBC.

On a positive note, the discovery may mean drugs used to treat cold sores could also prevent dementia, the BBC reported.

The findings were published in the Journal of Pathology.

Click here to read more from the BBC.