Jessica, I had client yesterday who was asked me about a problem a friend
was having with milk that smelled bad after even a short storage time (same
scenario:  stored in clean cont. handled properly, etc).  I asked if the
woman was using steroid nasal sprays, and the friend looked amazed.  Yes,
the woman has terrible allergies and uses an inhaler 2x a day for relief.
As these inhalers are safe for use in nursing mothers, there are quite a few
in use.  I keep meaning to look around for the ref. where I saw that sour
milk can be a consequence of this.  I believe it was in the US PDI.  I will
make an effort to remember to look it up today.
Barbara

Barbara Wilson-Clay, BS, IBCLC
Private Practice, Austin, Texas
Owner, Lactnews On-Line Conference Page
http://moontower.com/bwc/lactnews.html