The News Of The World reports that during last week's semi-finals the 34-year-old’s hair appeared “thick and bushy”, despite having apparently thinned in recent years.
"For the past few years Dec and partner-in-crime Ant McPartlin have had ever-rising hairlines and been unable to disguise it," an insider said. "But whereas Ant seems happy to grow older gracefully, Dec's hair seems to have regrown."
Other celebrities alleged to have had hair treatments include footballer Ryan Giggs and TV doctor Christian Jessen.
Gymnasts Spelbound were the eventual winners in the Britain’s Got Talent final last night.