Alex Horne’s reappearing hair

I just started watching this brilliant show and am in series 5. I’ve paused in the middle of episode 4, between commercial breaks of the sneezing task, because I noticed Alex’s hair goes from balding to normal. I searched the sub and Google for an explanation but couldn’t find one. Is this a normal oddity? The only thing I can think of was that this episode had contestants guess what changed in a scene while they were blindfolded and blowing up a balloon. Perhaps the audience is supposed to notice?