Humes was called back to Phillip Schofield’s side, having presented with him while Willoughby was hosting I’m A Celebrity last year, when Willoughby was struck down by sickness hours before going on air.
Opening the show, Schofield said: “You might have noticed that I’ve got a different co-host for the day.
“Holly’s poorly today. If you’ve been watching throughout the week you’ll know she’s been on a downward spiral.
“It started on Dancing On Ice where she wasn’t really brilliant on Sunday and it’s got worse and worse and worse, and finally she’s fallen over so she’s staying home today.”
He went on to wish his co-host well as Humes urged her to take a “duvet day” to recover before they got on with the show.
Willoughby was left in tears on Tuesday after telling a blind Manchester United fan that he would be an England mascot next month.
Declan Bitmead, who lost his sight after a severe reaction to amoxicillin, was overwhelmed by the FA’s invite to have him as mascot for the Euro 2020 qualifier game against Czech Republic at Wembley in March.
Schofield said: “You’ve taken it really well Declan, and your mum has taken it really well, but I’ll just get a tissue for Holly.”
Wiping tears from her eyes, Willoughby said: “Sorry it was your face when we told you. It was so nice.”
This Morning is on ITV, weekdays at 10.30am