1. It does not matter whether the phone is full of bacteria or not (almost everything is anyway). If you are worried about it, you just need to wash your hands

1. It does not matter whether the phone is full of bacteria or not (almost everything is anyway). If you are worried about it, you just need to wash your hands later on and avoid touching your mouth/eyes 2. If you don't want to hand your phone to a stranger, don't. If they hand their phone to you, it means they are ok with it. 3. Most of the time, when I am handling my phone to a stranger it's because I am in a foreign country, I don't know how to write something. There is a context behind it. I am not handing my phone and then moving away, so I can clearly see they are using my phone in the context.