Up until now, anyone who lived in the UK between 1980 and 1996 for more than a year has been not allowed to give a blood donation in Ireland.
But next month, from 7 October, that ban will be lifted.
The rule was originally imposed during an epidemic of Bovine Spongiform Encephalopathy, otherwise known as Mad Cow Disease.
In a statement, the Irish Blood Transfusion Service said the ban resulted in the loss of approximately 10,000 donors and has been a source of annoyance to those donors that they have not been able to donate since that date.
Professor Stephen Field is the Medical and Scientific Director with the IBTS.
Speaking on RTÉ's News at One he said a couple of donors in the UK transmitted a variant of the disease called Variant Creutzfeldt-Jakob Disease (vCJD) to recipients during that period, after the donors were thought to have contracted it through the food chain.
He said four cases were detected in the UK and that is why the rule was put in place.
Professor Field said in 1999 that scientists took the white blood cells out of the blood and there have been no cases since that measure was put in place.
"We call it leukodepletion, so leukodepletion has been an effective way in preventing the transmission of this disease as far as we can see.
"There has been no further cases and we felt that after a period of 20 years, from 1999 to the present, that it was appropriate that we looked at the science again," he said.
"And its been determined both here and in the UK that the risk is in fact a lot smaller than we thought it was. Its not absent, but its very, very tiny."
