In our recent trawl for questions we had several about insect repellents, especially in relation to Zika. Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito (A. aegypti and A. albopictus). Read more about Zika here http://www.cdc.gov/zika/transmission/ Most of the research on essential oils and mosquitoes used A. egypti, but there’s also some on A. albopticus. Turmeric oil does repel both for sure.
You may have heard that lemon-scented eucalyptus oil is especially effective, as effective as DEET, but this is not exactly true. The product that is in fact very effective is not a natural essential oil. Research showed that the most active repellent in Eucalyptus citriodora is p-menthane 3,8-diol (PMD), which is a very minor constituent. The product being used in insect repellents has about 60% PMD, which has been artificially boosted. I’m not saying you should not use it, but what I don’t want you to do is to buy a natural E. citriodora oil and think you’re getting something super-effective. It does work reasonably well, but so do many other oils.
Catnip oil is especially effective and relatively long-lasting, but it is rather pricey. Lemongrass, Cinnamon bark, Cassia and Clove are all pretty effective, but be extremely careful about using any of these directly on your skin. Peppermint, Turmeric and Citronella are safer for skin and about as effective. Some oils work better in combination than they do singly, for example Citronella and Eucalyptus globulus, Sweet Basil and Eucalyptus globulus, Cinnamon bark and Lemongrass.
Here are two formulations I would personally use to fend off unwanted Aedes. The first one would be safe to use on the skin or clothes and is safe in pregnancy. For toddlers substitute the peppermint with ginger oil. The other is recommended only to be sprayed in the air or vaporized. Avoid contact with skin.
You can use any type of base. In one study Olive oil was compared with Coconut oil as a base for essential oils, and Coconut oil was very much more effective.