A mom and baby in our practice have been dealing with thrush for months.
 They have gone through nystatin, diflucan, gentian violet etc.  Last week
this mom used tea tree oil and applied it with her finger to her baby's mouth
once a day for four days.  It has been a week now and no evidence of thrush.
 Her doctor was aware of  the treatment and was pleased with the outcome.
 The source of information used was a book called
How To Be Your Own Herbal Pharmacist
by Linda Rector-Page, ND., PhD.
 The description is as follows:
Part used: leaf.  Effective forms: oil extraction.  Therapeutic profile: an
extremely effective Australian herb with anti-fungal and anti-biotic
properties.  Primary uses: as a dilute solution for mouth  and gum problems,
and as a vaginal douche; externally, undiluted, as an anti-fungal agent for
warts, tumors, basal cell carcinomas, etc., dandruff, seborrhea, psoriasis,
and many types of skin conditions;  Secondary uses: as an insect repellant
and bite or sting healer, effective for both animals and people.

I was not the one who recommended this, she did it on her own but it did work
for her   so worth looking into.

Maria Parlapiano RN, IBCLC
the Lactation Resource Center, inc. in Chatham, NJ