Study summary
Efficacy of Unregulated Minimum Risk Products to Kill and Repel Ticks
Eisen L (CDC)
Read the original paper- Study type
- Review
- Year
- 2024
- Species tested
- Ixodes scapularis and other ticks
- Published in
- Emerging Infectious Diseases 30(1)
- Evidence strength
- Definitive evidence
How it was tested
A narrative review pulling together published field-plot acaricide trials and repellency studies that tested commercial 25(b)-exempt products against registered controls such as bifenthrin and DEET.
Summary
A CDC review in Emerging Infectious Diseases asking whether the unregulated minimum-risk botanical products sold to kill and repel ticks actually work, against EPA-registered products. Its verdict: efficacy is wide-ranging, often poor, and unpredictable, and real skin-repellency data for them barely existed.
Key findings
The exempt products were all over the map and mostly weak. Rosemary and peppermint yard sprays suppressed ticks 15 to 87% but faded within weeks, and cedarwood sprays managed only 5 to 6% knockdown, while a bifenthrin control hit 98 to 100%. For skin repellency of 25(b) actives at 10%, most oils (castor, corn, rosemary, sesame, soybean) lasted under 10 minutes, a middle group (cedarwood, citronella, geranium, lemongrass, peppermint, thyme) lasted 10 minutes to an hour, and only cinnamon, clove, and geraniol reached 1 to 2 hours. DEET protected for the full 6-hour test.
Limitations
The authors stress there were only three published evaluations of exempt repellent products, none applied to skin, and no laboratory data using the EPA-recommended human skin bioassay, plus tremendous variability even between products sharing the same active.