In response to Marie Davis:

Some months ago I got a call from a distraught mother whose infant had
"sores" in his mouth.  She called me to ask if these sores could be
infectious and be transmitted to her nipple.  She and baby had been to a GP
that day.  Per the mother's account, the Dr. told her that the sores were
either from a virus that would run it's course, or from the baby's sucking
too hard while breastfeeding (!).  Through a very long discussion, I found
out that this mother had had a terrible time with thrush (baby and breast)
with her first child and it was finally cleared up with gentian violet.  With
this new baby, when she thought that thrush might be starting, she
aggressively treated the baby with gentian violet (can't remember how much -
I think 3xdaily for 2-3 days).  I recommended that she D/C the gentian violet
and the ulcerations did heal.  The manufacturer states that gentian violet
can cause ulceration of mucous membranes.

Linda Englander, RN, IBCLC