Susan...I have been researching the "bloody sheet" issue extensively. It is a divided community, indeed. In the end, it is a matter of preference on the host's choice as to how to address the issue. Many say "let it go". And, from conversations I have read, while that camp vehemently criticizes the other...I cannot "let it go" and expect I may be verbally flogged for what I am about to share. C'est la vie! We each have liberty here. The most inspiring dialogue I read in another string made the point that blood is a biohazard and should be treated as such. This is the advice received directly from the Airbnb rep. I have had some pretty messy sheets and after extensive efforts to remove the stains I had to throw the sheets out (and yes, I used all the recommended methods: cold water, Oxyclean, etc. etc. etc) My husband said I never should have touched them at all. Unfortunately I did not have a security deposit in place and chalked it up to an expense and the hazards of the industry. I have since added a security deposit ($250) and I now respectfully mention it in my house manual and my welcome message as such:
"PLEASE NOTE: If anything breaks, spills, stains please let us know. Substantial damage to property or linens that are stained beyond repair (ie: blood stains which are a biohazard) will be charged against the security deposit (as described on your booking receipt). In such a case we will respectfully notify you. Thank you for understanding."
Then...if an "irreparable" stain comes into play, one host addresses the guest this way:
"Hi, thanks again for staying with us! It looks like there are some stains on the sheets and for everyone's health & safety, stained sheets need to be disposed of. Luckily, Airbnb's security deposit system makes it easy to add the replacement cost to your booking after we provide documentation. We've had this happen a few times, and guests are always gracious in handling it. If you'll approve the security deposit charges when we submit them, we'll be all set. Thanks again and all the best!
Also...I would never mention this in a review unless I was met with disrespect and lack of accountability on the guest's side. Then I think we owe it to the Airbnb community to leave a tactful review such as: "We would caution future hosts, as this guest refused to reimburse us for sheets that were ruined, after agreeing at the time of booking to approve documented charges for damage to our security deposit."
Now, I understand with your situation you do not yet have a security deposit in force. I would urge you to do so. It is only a "hold"....not an actual charge unless a claim is opened. Anywho...like you, before I had the security deposit in place, I expressed gently and respectfully to the guests that after extensive efforts to clean the sheets they had to be disposed of and replaced. And (sigh) they do not offer to reimburse and I don't feel comfortable asking because I had no such "house rule" indicated. But it seems such a no-brainer, out of respect, that one would graciously be accountable. But no. So...get your security deposit in place! And I think for your particular current incident you could leave a review similar to the one I quoted above, respectfully tailored to your situation. Be sure to preface it with the positives, though. Happy Hosting!