HOLY water from religious shrines - long regarded as having healing properties - could kill susceptible patients, according to the Catholic Herald.
The journal warns that the water, drunk by the sick or used to anoint wounds, is a breeding ground for infection. Germs are transmitted from people's hands or in bottles holding the water, the article, based on a study of holy water cultures.
Ms Linda Parsons, an infection control nurse at the Whiston hospital, Merseyside, England, who worked on the cultures said the contaminated water could have caused premature deaths.
"It could kill a susceptible patient," she added.
Mrs Parsons, who worked with microbiologist Karen Allen, said she was "quite concerned" by their findings.
Some hospitals have banned the use of holy water on wards, while the Whiston and the Royal Preston hospital, in Lancashire, now sterilise holy water, according to reports.
But such policies are accepted by the Roman Catholic Church, which considers such blessings as symbolic.
Father Paul Addison, a friar of the Order of the Servants of Mary, said such "sacramentals" were "reminders of a spiritual blessing and should not be taken literally".