I get that sometimes, if it's hot out and I've gone for a long ride. What seems to set it off is if I pee during the ride, that seems to irritate the delicate tissues more than normal. I may not feel it until I get in the shower, though. I do use chamois cream, but it doesn't always stop this.
My saddle is fine and I wear 2 different brands of shorts that I love. I just don't let the water hit me near those parts when this happens and definitely no soap near there, ever.
Tea Tree oil helps sooth this.