Commercial permethrin clothing lasts about 70 washes

Permethrin-treated clothing remains effective for roughly 70 washes if it’s factory-treated, but only about 6 washes if you spray it on yourself.

I’m talking about the real stuff—Insect Shield, ExOfficio Buzz Off, Craghoppers Nosilife—where they bond the permethrin to the fabric at the factory. Those last through 70 launderings before dropping below the EPA’s threshold. You won’t notice a cliff; it fades gradually.

DIY treatments (like Sawyer’s spray) are a different beast. They survive about 6 washes, or roughly 42 days of use, before needing reapplication. That’s if you’re gentle—cold water, hang dry. Tumble dry or hot water and you’re cutting that number in half.

The real trick is washing technique. No fabric softener, no bleach, no dryer sheets. Those strip permethrin faster than anything. Use mild detergent, dry on low or line dry. If you treat your own gear, reapply every season or after heavy use.

One thing nobody mentions: permethrin doesn’t repel mosquitoes—it kills them on contact. So you still need DEET or picaridin on exposed skin. The clothing is your backup, not your whole plan.

Wash it right and factory stuff will last years. Spray-on needs a yearly refresh.