I was born in the 60s, my mum used a dishrag, there wasn't antibacterial anything, we ate mud pies, played in each others houses and had baths instead of showers.
I rarely get a cold, never had flu that I know of, apart from 3 days in 2004 when I got vertigo and couldn't stand up I haven't had a day off work sick in 20 years.
Google search result said:Immune problems, contrary to popular belief, do rarely manifest themselves as frequent colds. Other symptoms like fever, weight loss, chronic diarrhea, pneumonias are typical of immunological defects.