As Strawberry and others are saying, please please let the escort know if you are planning to use this.
I've had personal experience of someone using a delay cream without telling me, it was very unpleasant and he was very lucky I didn't have a worse reaction to it, the effect isn't immediate when you are giving a bj, it takes 30+ seconds to kick in and builds the longer you are in contact, there is very little discernable taste. My mouth became numb and tingly, my tongue felt like it was swollen and was totally numb, like a whole mouth dental visit.
As soon as I realized I stopped and questioned him, at which point he admitted that he had used it because he was nervous and don't want to cum too fast.