Diane:
why an antibiotic and cortisone combined worked when either alone did not:
Cortisone, and other steroids are anti-inflammatory.  They work by
disorganizing microtubule structure in macrophages (white blood cells that
'eat' germs and other cells.  Macrophages 'walk' through the body using their
microtubules to form 'legs'.  If these cells cannot 'walk', they cannot
congregate in the affected area, and cannot release all the lymphokines
(chemical messangers) that draw other white blood cells to the area, open up
blood vessel pores (to allow their friends to get out into the tissues),etc.
These lymphokines are responsible for the redness and itchiness or pain of
rashes.
Now, IF the inflammation was triggered by a germ, upsetting the immune
response as above will make the germ worse, which makes the body pour more
resources into the area, overcoming the dose of steroid.  So the rash stays.
When you use both, the antibiotic polishes off most of the germs, the steroid
stops the inflammatory reaction, and the rash disappates.
        This is slightly oversimplified, but it makes the point.
Catherine Watson Genna, IBCLC  NYC  [log in to unmask]