Scanlon, who races professionally with the AG2R Prévoyance team, is suffering from a viral infection.
The Sligo man has struggled since winning the last stage of the Circuit des Ardennes in April and, after a series of tests, has been advised to take a break.
Scanlon will be expected to be amongst the spectators for the record field of 200 riders from Norway, Canada, Estonia, the Czech Republic, Germany, Netherlands, America, Britain, Scotland, Wales and 17 county teams,
John Dempsey has been named as Scanlon’s replacement. The Tipperary rider has had an impressive season, including wins in the Rás Mumhan and the first stage of the Tour of Ulster.
He will join Paudie O’Brien, Conor Murphy, Brian Keane and Stephen Gallagher. Gallagher was drafted in after Paul Griffin withdrew due to contractual difficulties with his Giant Asia team.
The race will start from the GPO at 12:30 on Sunday and following stage finishes in Emyvale, Tubbercurry, Lisdoonvarna, Templemore, Abbeyleix, Rathdrum and Wicklow Town, the event finishes in the Phoenix Park at 3pm on Sunday, May 29.