The explanations given for how it works do not appear to me to be scientifically based.
I'm interested in midge repellents, as we have a lot of the $%£&?! round here and a day after exposure I look like the elephant man.
Most of the research has been done on mosquitos (Anopheles spp.) and not midgies (Culcoides spp). For mosquitoes the research shows DEET is best. May be toxic for children and it melts plastic. 3M make a new formulation of DEET called Ultrathon which is supplied to the US military. Allegedly it is nicer to use and more effective than plain vanilla DEET.
I personally have found DEET not very good against midges.
One trial of the herbal repellant Mosiguard found it about as good as DEET against midges. I've not tried it.
DMP is an older repellant (Brand name Shoo I think). I've found it useless.
There are a number of other herbal ones based on plant oils.
Mozzyoff cocktail is one. So far it is the best I've tried. It is an oil. I like the smell off it but many don't.
http://www.mozzyoff.com/testing.htm
India tree is another. It contains Neem oil. I plan to try it soon.
More info at:
http://www.albawest.com/repellents.html
I would quite like to conduct some trials. We could randomise one arm of each volunteer to a different repellent and then count the bites.......