There was a report in ACTA PAEDIATRICA, 1994 Vol 83 p 683 by Rosti et al,
entitled 'Toxic effects of a herbal tea mixture in two newborns'.  Apparently
the mothers were drinking 'large quantities' of a herbal tea which was supposed
to increase milk supply.  The tea contained liquorice, fennel, anise and galega
officinalis.  According to the report I saw, fennel and anise both get into
breastnilk, and they contain essential oils which can cause 'neurological
symptoms'.  The 2 babies who were the subject of the report were aged 15 and 20
days, and had been vomiting, became lethargic, had weak cries and poor sucking.
One of the mothers also said she was drowsy and weak.  Babies and mother rapidly
improved when the teas and breastfeeding were stopped.  Breastmilk was restarted
after 2 days, and both babies were fine.

Just a word of caution, to add to all the rest....

Mary Broadfoot,  Paisley, Scotland