Blocked Scent Glands
If you purchased a de-scented baby ferret the anal scent glands will already have been removed. If not you will have to check for the special problems that may ensue.
An unpleasant odor from your ferret that lasts only a few minutes is probably due to blocked anal scent glands. Although it is normal for a ferret to release these glands when it is very frightened or during the breeding season, it is not normal for the animal to release them at any other time.
If the ferret is releasing its scent glands when it shouldn't it is time to visit the veterinarian. They will probably evacuate the scent glands and administer an antibiotic because an infection is probably present. If this treatment does not clear up the problem the ferret will have to be de-scented, in other words have the scent glands surgically removed.