@Tony-And-Una0
That is unfortunate but with hosting it is always a possibility, you just don't know the capabilities of those who stay with you and you must protect yourself.
My reaction would be to follow Susan's advice and have the mattress professionaly cleaned. This will not only remove the damage from this guest but, as your mattress has been unprotected it will have built up a sizeable quantity of skin cells and professional cleaning will return it to good hygenic condition.
I am sure the guest would be happy to meet you on the cost of cleaning because all you are asking them for is a re-instatement of what you already have.....you are not asking for anything new!
You must have a mattress protector. I spend a large sum of money on our listing bed and I actually have two mattress protectors on it.....one a good quality one and the top one a cheaper terry towelling version. With over 300 hostings and many little 'accidents' nothing has ever made it through to the bed itself. After each guests I wash everything down the the main mattress protector for each guest. I also have pillow protectors which get washed between every guest along with the pillowcases. I would never, but never expect a guest to sleep with their head on someone elses dribble....particularly after they have had a few red wines!!!
Tony and Una, you do learn the hard way but now is the time to protect your investment, protect your bed!