Study summary
Efficacy of unregulated minimum risk tick repellent products evaluated with Ixodes scapularis nymphs in a human skin bioassay
Burtis JC, Ford SL, Parise CM, Eisen RJ, Eisen L (CDC)
- Study type
- Lab
- Year
- 2024
- Published in
- Parasites & Vectors
- Evidence strength
- Well-supported evidence
Summary
CDC human-skin bioassay comparing EPA-registered DEET against unregulated 25(b) botanical tick products on blacklegged-tick nymphs, hourly from 0.5 to 6.5 hours.
Key findings
25% DEET held about 98% repellency across all timepoints through 6.5 h. The pooled 25(b) botanical products fell from ~86% repellency at 0.5 h to ~40% at 1.5 h to ~2% (no better than the ethanol control) by 2.5 h, with none effective from 2.5-6.5 h.
Limitations
Single human subject; tests finished retail products at their label concentrations (often low or mixed), so underperformance partly reflects formulation rather than the pure active; crossing endpoint, not attachment/bite.