Study summary
Formulations of Deet, Picaridin, and IR3535 Applied to Skin Repel Nymphs of the Lone Star Tick (Acari: Ixodidae) for 12 Hours
Carroll JF, Benante JP, Kramer M, Lohmeyer KH, Lawrence K
Read the original paper- Study type
- Rct
- Year
- 2010
- Sample size
- 17 subjects
- Species tested
- Amblyomma americanum nymphs
- Published in
- Journal of Medical Entomology
- Evidence strength
- Well-supported evidence
How it was tested
A 5-cm band of repellent was applied around each volunteer's lower leg, and 70 tick nymphs were released below it at six time points from 2 to 12 hours, counting how many crossed the band.
Summary
A skin-band study of how well five repellent formulations stop lone star tick nymphs from crossing treated skin, retested every two hours out to 12 hours. Any product with at least 20% active held up all day; a 10% IR3535 lotion did not.
Key findings
The higher-concentration products, 20% picaridin as spray and lotion, 20% IR3535 spray, and 33% DEET cream, kept fewer than about 6% of ticks crossing at every challenge, with no decline over 12 hours. The 10% IR3535 lotion, at half strength, let far more through, around 18%. Beyond blocking crossings, all the repellents also drove 40 to 55% of ticks to fall or crawl off the volunteer entirely, versus about 11% on bare skin.
Limitations
Colony-reared rather than wild ticks, only light activity by volunteers so real sweat and abrasion could shorten protection, and no shared placebo vehicle, so the control was bare skin.