I used a piece of permethrin treated soft Tyvek (one meter by two meters and a bit) on the Camino and had lots of questions about it. Could have easily sold it in Santiago two weeks ago but gave it away to someone who will make good use of it.
I have used permethrin in Africa for that past several years to keep the mozzies at bay. Sprayed my clothes, liner and bed net, and couldn't smell or feel a difference. Had to re-spray from time to time as the permethrin doesn't last forever.
This site is run by Ivar at in Santiago de Compostela.
This site participates in the Amazon Affiliate program, designed to provide a means for Ivar to earn fees by linking to Amazon