It's very easy to make your own natural mosquito repellent. These natural products will effectively repel mosquitoes, but they require more frequent reapplication (at least every 2 hours) and higher concentrations than DEET. Because of the differences between types of mosquitoes, products that contain multiple repellents tend to be more effective than those containing a single ingredient. As you can see, natural repellents tend to be volatile plant oils.
Citronella Oil
Lemon Eucalyptus Oil
Cinnamon Oil
Castor Oil
Rosemary Oil
Lemongrass Oil
Cedar Oil
Peppermint Oil
Clove Oil
Geranium Oil
Possibly Oils from Verbena, Pennyroyal, Lavender, Pine, Cajeput, Basil, Thyme, Allspice, Soybean, and Garlic