Permethrin works and works very well! I use those sawyer spray bottle and spritz the underside of my hammock. The times that I had not used permethrin, mosquitoes bite through the hammock and shirt. In the morning, I have probably been bitten a hundred times on my back. One good spray is enough to last over +6 trips from my testing, didn't notice any reduction on its efficacy in chasing away mosquito. I would still advice netting though in infested areas, they can still bite you from the top.