why do dogs like to sniff dirty underwear or even eat the crotch out of them?

Because it contains your scent . A dog walking around with a piece of your clothing (whatever it may be) in its mouth is like him/her carrying your picture around with him/her. They only reason they chew it up is because they enjoy chewing.

Its because the world smells very different to a dog than to us. A dog's nose is about 100 times more sensitive than ours. This means that when we smell something foul, we are only picking up the principal odors, like sulfur or ammonia. A dog probably picks up on several hundred other principal odors that are appealing to it. And chewing stuff is an instinctive behaviour with all dogs.

They sniff each others backside to say hello.... your undies smell like you - extra strength!! It not going to just stop its they're nature. They may be chewing it up to get rid of it. They don't like 'messes' in their 'dens'. Or the maybe its like a smelly bone?! A hamper would be a good thing to invest in ... a tamper-proof one.

Because they probably contain ammonia which attracts a dog, the solution is to bathe more and change your undergarments regulary preferably every day :)

dog like to do that because that is the way they identify you and anyone they meet. they usually sniff your bottom when they first see someone new.

I'm a guy, dogs don't eat my underware. I think this is a girl thing. sorry i can't help. You could teach them what is thiers and what is yours, that might keep them from doing it.

Because people are nasty,filthy things apparently.

i whish i knew!!!!!!!my rat terrier chew my underwear!11

i dunno, but when you find out let me know.