Does Washing Reduce the Effectiveness of Permethrin-Treated Clothing?
Protection is strongest when new
Effectiveness declines with washing
Still better than untreated clothing
Tick contact time matters
Permethrin-treated clothing can repel and kill ticks—but its effectiveness decreases with wear and repeated washing.
A study by Connally and colleagues examined how wearing and washing affect the ability of treated clothing to repel and kill Ixodes scapularis (blacklegged tick) nymphs.
How the Study Was Conducted
Investigators exposed ticks to Permethrin-treated clothing for 30 to 120 seconds and then monitored their behavior on treated and untreated textiles.
This allowed researchers to evaluate both:
- Contact irritancy (repellency)
- Toxicity (ability to impair or kill ticks)
Best Protection Occurs Before Washing
New (pristine) Permethrin-treated clothing provided the strongest protection.
“Pristine Permethrin-treated clothing displayed strong contact irritancy and toxicity toward I. scapularis nymphs,” writes Connally.
After one hour of exposure:
- Only 0–30% of ticks showed normal movement
This indicates substantial impairment or death of ticks after brief contact.
Effectiveness Declines With Washing
After 16 days of wear and 16 washing/drying cycles:
- Permethrin levels dropped by 50–90%
This reduction was associated with decreased tick-killing and repellent effects.
After one hour of exposure:
- 31–67% of ticks showed normal movement
This indicates reduced—but not eliminated—protection.
For prevention strategies, see Lyme disease prevention.
Still Better Than Untreated Clothing
Even after washing, treated clothing performed better than untreated garments.
- Untreated clothing: 90–100% of ticks showed normal movement
Washed Permethrin-treated clothing still provided partial protection.
What About Socks and Shoes?
Results varied depending on the type of clothing:
Socks:
- Less effective than other garments
- Possibly due to looser weave and reduced contact with ticks
Shoes:
- Remained effective when worn but not washed
The structure of the textile appears to influence how well Permethrin is retained and how much contact ticks have with treated surfaces.
Important Limitations
The study highlights several practical limitations:
- Ticks may reach skin in less than 30 seconds
- Ticks that attach directly to skin are not affected by clothing
- The study did not evaluate human exposure risks to Permethrin
Clothing is one layer of protection—not a complete solution.
Clinical Takeaway
Permethrin-treated clothing is most effective when new, but protection decreases with repeated washing.
Even after washing, treated clothing remains more protective than untreated garments—but should be combined with other prevention strategies.
Related Reading
- Permethrin-treated clothing and the “hot foot” effect
- How to kill ticks on clothing
- Lyme disease prevention
References
- Prose R et al. J Med Entomol, 2018.
- Connally NP et al. 2018
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
I live in SE Pa, my dear daughter has had Lyme disease with bullseye rash and other symptoms twice, and once with Neuroborreliosis symptoms and highly positive 2 tier serology and Western blot for IgM and IgG. She has never recovered fully from her 3rd bout. I urge everyone in highly endemic areas like mine to wear permethrin treated clothing, though it may not work 100% and though I, too, do not like the idea of wearing pesticides- the alternative of Lyme or other tick-borne disease is worse. I watched a deer tick struggle and die on my permethrin treated socks while gardening and it was very satisfying.