Can eating crisps after mononucleosis kill me? (my doctor recommended me liver diet.)

No, they won't kill: I do know that it is very important to eat as healthy and nutritious a diet as possible after mono to prevent chronic fatigue and strengthen your immune system. So, eat lots of veggies and fruit - good sources of protein (liver's one) and avoid sweets, fatty foods and empty calories as much as you can. It is not a major crime to eat some fun snacks - just be very moderate and infrequent. Get well

Crisps: Having lived in Europe - I am assuming that you are referring to what are called potato chips in the US. I would not live only off of crisps. If you have really swollen tonsils and painful throat - crisps could be painful going down. No crisps will not kill you. But do try to get in some nutritious and substantial food too. If you doctor recommended liver - then would follow guidance. Take care.