We ourselves have not experienced blackheads on ears, though we do have a
adrenal gland survivor, who still hasn't grown all his hair back, and
still gets blackheads..
 
but, I just wanted to suggest that maybe (only maybe, and only from my
experiences with some cats) you may want to investigate further IF, and
only IF, your ferret gets more sunshine then most do..not trying to scare
you as this is remote.  But, some of the cats we owned when we were young
had very light coloring and or were simply pure white, and use to get
sunburn on the tips of the ears..  which lead to small scabs ( blackhead
looking things) which were infact sun cancers..  not saying this is the
case... just that I wanted to raise the issues of ferrets and the
possibilities of too much sunlight..
 
and the fact that they are not "daylight" animals..especially albino's
 
however, I would also consider, things such as ear mites, and or just
plain "scabs" from fighting ?  if you own other ferrets and they
playfight a lot, "some" have a tendency to bite ears.
 
only some thoughts, as I have notyet experience blackheads on ears, so
there may be many other reasons..
 
Darrin
[Posted in FML issue 4688]