I've often wondered this myself. Not really sure though? There is a video on YouTube of Ian Heaps fishing bread. He says his Dad always found an Ivy leaf and rubbed it over his hands before fishing to get rid of any human smell. Makes sense in theory?
I never put diesel in the day I go fishing ,and I’m paranoid about the fact that I smoke , I’ve got a lot of small atomiser bait sprays, I like to spray some on my fingers and rub that in ...I think scopex or tutti fruity is better than nicotine tainting the bait