Here are ideas from various sources about insect repellents...
From Tom Brown: "Grandfather had always said that the natural diet of survival would make us tasteless to insects, and, judging from the soldier's antics, he was right again. I could not remember the last time I had been bitten by anything." From pages 134 and 135 in The Way of the Scout.
Take a hand full of wild onions, or wild leeks, and rub them between your hands until you get the juices out. Use like bug repellant. It doesn't smell the best but it works.
In an extreme situation cover exposed areas of skin with mud.
Burn smudge sage, or incense....the smoke really keeps them away....and funny, it didn't keep
the other critters away
A smoky fire (use green plant material)
If you are only eating foods native to that area you don't smell as interesting to them.
Eat cloves of garlic every day. Keeps people away as well.
Vitamin B1
Cedar smudging is supposed to drive insects out of the debris hut, so smudging your clothes may help.
I was walking in the woods down at the James river the other day. The tiger mosquitoes were swarming me. I tried rubbing some spicebush berries on me. They really didn't seem to help so I grabbed some leaves of a nearby jewelweed plant and rubbed the juice over my body. The mosquitoes left me alone. The next day I was back and got a whole jewelweed plant and rubbed it on me. It wasn't nearly as effective, but did reduce the bites some. Today I was at the river again and the mosquitoes were swarming me. This time I used just leaves from some smaller plants and it worked, until I went swimming which must've washed it off.
Eating a lot of black pepper works great. Most bugs HATE the smell of black pepper
Another bug repellant that is in common use by treeplanters in Northern Ontario (outside all day in one of the buggiest places on earth) is oil or grease. Applied to the skin it works wonders. Mosquitoes, blackflies and no see ums can't bite through it (it clogs their mouthparts) and in some cases they get stuck and drown.
A trick that is regularly employed is to reduce the amount of clothing you wear to the bare minimum so that the insects don't crowd your face (lots of exposed skin on your back for them to land on, only its protected with oil.) I used this method for 6 seasons and it was better than DEET!
Just don't forget sun screen.