Call me crazy, but if I were a sex worker and my income could be seriously disrupted if I contracted a STI, staph, or mrsa infection, I doubt I'd be interested in interacting sexually with a dude with open rashes, random skin conditions, and so on. Easy for you to write off the risk of your condition(s) on behalf of someone else.
And a piece of paper that is at best a snapshot in time, and might not even be accurate the day of depending on timing, wouldn't exactly fill me with confidence either. Especially if you have a nasty skin condition that isn't an STI.
Just get your conditions cleared up before putting others at risk for whatever you might have, pretty simple.