Happened to me last week too. Right after my shower and having paid $250 the girl said she was "just finishing" her period, so suggested daty was not a good idea.
I told her that being on her period at all is a complete no-go for me. She actually said "some guys don't mind". I asked for my money back, and she first gave me $150. I said what about the other $100? She said "oh yeah" and gave that back as well.
I told her it's unfair to the client to work as an escort on your period , as exposure to menstrual blood even with a condom on will turn off most guys, and is possibly a health risk for them.
I texted the agency to tell them why I left, and the booker said she had no idea that the sp was on her period.
That said I know that a lot of spa mpa's will work on their period, using a sponge or a tampon to block the flow. I guess the assumption there is that no activities will take place that will be affected by that. I do remember a long time ago that I left a session at a spa when the girl, who I had seen a few times, warned me she was on her period, so no daty. The next time I saw her she told me the spa receptionist management was pissed that she had told me that.
Another time 2 weeks ago when I entered the condo I saw the girl had a cold sore on her lip. I asked what it was. She said it was a cold sore, and showed me a vial of "antibiotic" pills she said she had been taking for 2 weeks to get rid of it. I said maybe the pills are anti-viral, as antibiotics are ineffective against the herpes virus that causes cold sores. I also scolded her for working with an active oral herpes infection
Again I left immediately. When I texted the booker she said the girl texted her after I left and said it was "just a pimple". When I told the booker that the escort called it a "cold sore" to me, said she had it for 2 weeks, and was taking pills for it, the booker just replied "oh".
I don't blame the agencies as I don't think they were made aware of these issues by the ladies involved. But "Hey, let's be careful out there..."