Why is lavender tea generally advised against consumption for breastfeeding women?

Unknown if components pass into breast milk affecting the infant

The primary directive for breastfeeding women to avoid lavender tea stems from a lack of comprehensive safety studies concerning lactation. It is currently not established whether the chemical constituents present in lavender, which are ingested by the mother, are transferred into the breast milk. Furthermore, if these components do pass into the milk, their potential effects on a developing or nursing infant are entirely unknown. Since there is no established safe threshold or dosage for an infant absorbing substances via breast milk, the most responsible and widely accepted course of action is complete avoidance during the entire period of lactation to mitigate any unforeseen negative consequences for the baby's health or development.