English lavender has traditionally been used as an antimicrobic or as an adjuvant in mood disorders, such as restlessness or insomnia.27 While an in vivo study on rats showed CYP2D6 inhibition and CYP2A induction,56 a small in vivo study on humans did not report significant P450 cytochrome interactions after the administration of an oral extract of lavender for 11 days.57 This evidence concerns the gene CYP2D6 and insomnia.