To b brutally honest. Its not about safe, its about freshness. Ur talking about a girl havn sex a lot of the day with several diff fellas. Some escorts r extremely smelly(im not sayn all the time) n that strong salty taste is very off putting.
I normally do the finger test to check, mite make me sound like a dickhead, but it let's me know usually wot I need 2 know. Going down on escorts is not a big thing 4 me.