Free Bug Spray

Just dig a hole with water in it and mix up some mud and use it either for fun as a mud bath, or use it as bug repellent. The theory is to make your body unappetizing to the insect, in other words mask the human scent with a scent that insects naturally avoid. This can also be done with foul smelling natural chemicals or smoky clothing and smoky skin. I have a theory that would still need to be tested, which is that ashes from a fire would be a good insect repellent from acidity and being smoky. Some repellents have to be reapplied after certain periods of time from natural sweating and rubbing off.
Lemon grass is a genus of plant that has some species that are natural insect repellent plants such as Citronella Grass, and some species that are edible. It didn't say on the lemon grass page whether or not all lemon grass species are edible. It didn't say if some species are just unpalatable, or if there are actually some that are bad to eat.
But bug repellent is mainly used in undeveloped areas. Some sand flies in sub tropical areas carry leishmaniasis and this can either be avoided by wearing insect repellent or avoiding the type of area where these parasites exist. Wiki says that this disease only exists in areas where there is a population of small mammals such as rodents, or canine, or bats, that the sand flies get the parasite from. So avoid the deserted islands that have small rodent populations carried over by Spanish explorers. Or just wear an insect repellent such as mud or Deet.
But for mosquitoes you can get malaria or yellow fever in undeveloped countries still but only because the people in those countries are too poor to afford drugs such as quinine or the vaccine for yellow fever to cure themselves. Also mosquito nets are good for when you sleep.
But still you may just decide to stay away from undeveloped areas to never get infected with any parasites. But if you're planning on being an explorer, or adventurer, or traveler this info should prove helpful.