Three molecules found in rosemary or nutmeg essential oils repel ticks (Dermacentor variabilis) more effectively than DEET in a no‐human assay

BACKGROUND Development of new personal repellents to prevent tick bites is progressing to keep up with the increasing threat of tick‐borne diseases in humans. However, the market share of natural, plant‐based repellents is still quite small. We tested all of the major (>1%) components found in the essential oils of rosemary (Spanish variety) and nutmeg. These were tested with Dermacentor variabilis ticks, a robust tick capable of vectoring human diseases, in a no‐human horizontal Petri dish assay. For comparison, we also tested the active ingredients currently recommended by the CDC and EPA as personal repellents for use against ticks. RESULTS Of the 16 oil components tested, three performed significantly better than N,N‐diethyl‐meta‐toluamide (DEET) in our assay. These compounds were myristicin and safrole found in the nutmeg oil, and terpinolene found in nutmeg oil and as a minor (