If Fido has developed a crotch-sniffing fetish, correct his behavior, because it can be embarrassing to the objects of his affection. With about 220 scent receptors, your dog's nose is an investigative tool that provides information about the people he meets. Women especially might fall victim to Fido's crotch sniffing, because of constant pheromone changes that occur during their menstrual period, when they're ovulating and after giving birth. With persistence and patience and plenty of dog treats you can redirect Fido's attention so he forgets all about sniffing crotches.
Inform your female friends that you're trying to break your dog's crotch-sniffing habit. Invite them over to your house so they can help you teach your dog right from wrong.
Put a collar and leash on your dog and tell him to sit and stay while you're waiting for your female friends to arrive. When he obeys, give him a treat to reward him for listening.
Jerk the leash or loudly clap your hands and say "leave it" when your dog gets up to satisfy his sniffing urge. Put him back in his place and firmly say "sit" and "stay," then reward him with a treat when he obeys. Alternatively, show him a dog toy to distract him after the leash correction and praise him when he shows interest in the toy. Repeat this tactic each time your dog starts sniffing -- don't allow him to get away with it.
Step forward and say "leave it" or "no" if you're the object of your dog's affection. Your pet companion will be forced to stop sniffing and move out of your way. Offer him a dog toy to play with and praise him when he shows interest in it. Avoid stepping backward when your dog starts sniffing, because this is submissive behavior, which might give him the impression that he's your superior.