If you don't want to use DEET to keep the mosquitoes away, lemon eucalyptus-based repellents actually do a pretty bang-up job. Here's a way to make your own spray at home and keep those bloodsuckers away.
This video from the HouseholdHacker YouTube channel explains how to whip up your own homemade mosquito defence. All you need is lemon eucalyptus oil, vanilla extract and some witch hazel. The menthoglycol in the lemon eucalyptus oil has been shown to be almost as effective as DEET at repelling mosquitoes, the witch hazel acts as an emulsifier and the vanilla extract makes the spray smell nice.
Add around 30 drops of lemon eucalyptus oil to your mixing container, followed by one teaspoon of vanilla extract, and 110g of witch hazel (you can also use rubbing alcohol, vodka, or cooking oil). Mix it all up and pour it into a spray bottle and your homemade mosquito spray is ready.
The repellent should work for about four hours before you need to re-apply.