At the camp practically everyone of us were attacked by Midges. Patchouli was the most used and seemed pretty effective at keeping them from biting. I just did a search for essential oils as insect repellent and indeed Patchouli is considered effective against Gnats (are they the same as Midges?)
Further reading of the website informs me that peppermint water is effective at killing houseflies. Flies have been bugging me for ages. We have fly spray, but I am reluctant to start spraying it around. You can regularly see me running about the house with a tea towel or similar trying to knock the buggers out of the air. This is often accompanied by swearing.
Anyway, the website: http://www.raindroptraining.com
Popularity: 28% [?]
tea tree and citronella are also pretty useful, you can dab tea tree directly onto your skin (assuming you aren’t sensitive to it!) and it also repels cat fleas so you can flick it at the cat if you are of an evil disposition and like watching cats with really disgusted looks on their faces when they clean it off!!!!