The former Spice Girls singer received a negative reception from the crowd for insulting a contestant in his 80s.
[Mel B photographed on the first day of 'X Factor' auditions in Manchester]
Lou, who is an 81-year-old widower from Birmingham, is the oldest contestant in the current series and reportedly opened his audition by saying that he was "available" for regular X Factor panelist Tulisa Contostavlos.
Contostavlos said that Lou's performance "pulled at my heart strings" but Mel B was not won over, saying: "I wanted to fall asleep".
However, Mel B comforted a woman who began to cry following her audition during the first session. She was helped up and down from the stage by Gary Barlow, apparently struggling on the steps because of the large heels on her shoes.
Barlow was the recipient of teasing from Louis Walsh - who referred to him as "Sir Gary" during the day's auditions - and received salutes from members of the audience when 'Rule Britannia' was played during the day's second audition session.
Auditions for The X Factor continue at EventCity in Manchester today and tomorrow (June 6 and 7).