Doctors advised Dennis to rest due to an illness he has been experiencing over the past few days.
As per Strictly rules, Dennis and his professional partner, Dianne Buswell, will receive a bye to next week's competition.
Buswell shared her support for Dennis on Instagram, calling him a 'trooper' and expressing hope for his return next week.
This marks another setback for the series, following previous withdrawals from contestants Dani Dyer and Kristian Nairn due to injury and medical reasons, respectively.