NOTE: The effective oral dose of Lavender oil is suggested to be 20–80 mg per day,5 the equivalent to 1-4 drops per day. Excessive oral intake of Lavender oil has been reported to cause nausea and drowsiness.5
If Lavender is ingested orally, it must be a therapeutic food-grade oil; otherwise, even with oils marketed as natural, organic or pure there is still risk of impurity or adulteration of the oil that renders it harmful for ingestion. Moreover, ingestion of essential oils should be done under the close supervision of a doctor and a certified aromatherapist; some essential oils can interact with medications or exacerbate medical conditions, and can even prove toxic taken in large quantities (just like any drug would be).
There is suggestion that weak estrogenic and anti-androgenic activities of Lavender oil may contribute to an imbalance in estrogen and androgen pathway signaling with excessive topical use.5 Lavender acts as an endocrine disruptor, elevating estrogen and inhibiting male androgen.