OK, a slightly disgusting if practical topic:
Especially after walking in long grass, it happens frequently that I get bitten by mites. Little spider-like animals that make a home under your skin and itch like HELL. See
Wikipedia for the gory details. For example, under the soles of the feet, on the ankles and kneecaps.
I got those bites every year from playing outdoors volleyball, and now found out more or less by accident that
Permethrin ("Nix" from the pharmacy) is freely available and very efficient to kill the little s*ckers, especially in combination with a little "needlework" to expose them.