My husband and I were having a disagreement about his children visiting us for the weekend while they have the flu. My mother-in-law told me that I was being ridiculous not wanting them up because 'germs don't exist'. What proven scientific facts do your relatives and friends refuse to believe?

My youngest daughter has earned the lead part in the school play and she is very proud of herself. Her play is this week and knowing that the kids had the flu, I wanted them to wait until next weekend to see us.

I didn't want to make everyone in our house sick unnecessarily. My husband disagreed (of course he's not the one who has to clean up vomit....) and my mother-in-law then took his side. Saying that germs 'don't exist' and 'kids only get sick from not eating properly.' She also claims that all the health problems attributed to smoking are complete and total fiction.

What scientifically proven facts do your friends and family refuse to believe?