This is for Lotsachicken - Definitely have your dog checked for thyroid problems. It is common in dachshunds and your mention of little hair and bald spots fits in with that. Dachshunds should not smell bad unless they roll in something. That's one of their positive traits - lack of "doggy odor" I've had many dachshunds since I was 5 years old and none of them have ever had general bad body odor even with very infrequent bathing and spending lots of time outdoors.
