I too have heard the concern about gentian violet.  So I tried to find
the source of that concern.  The concern seemed to originate with the
UK Food Advisory Committee's "Final Report on the Review of the
Colouring Matter in Food Regulations 1973" where they quoted a study
about gentian violet's carcinogenicity.  It was not easy to get this
report.  The Hospital for Sick Children library put in a search for
this report, and finally after a few months got a copy from a small
library in Missouri, with the note that nobody has ever asked for this
before so please keep it.

I found the reference after another few months.  It too came from a
different small library in Missouri.  It came on microfiche, also with
a note, to my amazement.  "No one has ever asked for this before so
please keep it."

The study was this:  They fed rats gentian violet 100-500 mg/kg/week
for their entire lives, and some developed liver tumours, of a type
which I have never heard of ever occurring in humans.  It's on
microfiche and I don't have a reader so I can't check it out now.

Now, 1% gentian violet contains 1000 mg of the crystal/100 ml.  When a
mother uses the gentian violet as I suggest, she buys about 10 ml, and
at the end of the treatment she usually has 7 or 8 ml left.  For the
sake of argument, let us say the mother uses 5 ml.  This means the
baby will have gotten a maximum of 50 mg of gentian violet (actually
less, because some is on his clothes and on mother) in a three or four
day period.  If the baby weighs 5 kg, he got 10 mg/kg for the total
treatment.  If someone wants to document it further, they can soak a
few hundred ear swabs in gentian violet and weigh before and after and
figure out how much the baby gets with each application.

I, for one, will continue to use gentian violet and a pox on the rats.

Jack Newman, MD, FRCPC