Study summary
Protective effectiveness of long-lasting permethrin-impregnated clothing against tick bites: a randomized controlled trial among outdoor workers
Mitchell C, Dyer M, Lin F-C, Bowman N, Mather T, Meshnick S
Read the original paper- Study type
- Rct
- Year
- 2020
- Published in
- Journal of Medical Entomology 57(5):1532-1538
- Evidence strength
- Definitive evidence
How it was tested
Randomized controlled trial of factory-impregnated permethrin clothing among outdoor workers over two seasons, measuring tick attachment rates.
Summary
A randomized, placebo-controlled, double-blinded trial testing whether factory permethrin-treated work clothing actually cuts tick bites for people exposed on the job: outdoor workers in Rhode Island and southern Massachusetts, a high-Lyme region. One group wore treated clothing, the other identical untreated clothing, and neither the workers nor the researchers knew which was which.
Key findings
Treated clothing cut tick bites by roughly half to two-thirds. In the first year bites fell about 65% (0.13 versus 0.37 per 100 work hours) and in the second about 50% (0.25 versus 0.50), a combined two-year reduction near 58%. This is the strongest controlled evidence that permethrin-treated clothing protects real people doing real outdoor work, and it is why treated clothing paired with a skin repellent is the standard tick-country recommendation.
Limitations
Bites were self-reported, and the authors could not always confirm a bite happened while the worker was actually wearing the treated clothing rather than off the clock. Ticks can also land on exposed skin and never touch the fabric. The trial covered one region with 82 workers, so the exact figures may not transfer everywhere.