You should never, ever have a slice of lemon in your drink. Here’s why ‘ice and a slice’ is a bad option:
Philip Tierno is author of “The Secret Life of Germs”. He says that his tests on lemon slices always come up with evidence of contamination from human skin and other contamination.
That’s because – before a slice appears on the rim of your glass – several people are touching the lemon, handling it, cutting it, placing it in a container, then picking it up at a later point. Lemons are rarely washed before use in drinks, and hand-washing is not practiced very well by many bartenders.