The essential oils that work well against mosquitoes are:
lemon eucalyptus oil
Safe carrier oils and alcohols include:
any other cooking oil
Natural Mosquito Repellent Recipe
Mix the essential oil with the carrier oil or alcohol. Rub or spray the natural insect repellent onto skin or clothing, using care to avoid the sensitive eye area. You’ll need to re-apply the natural product after about an hour or after swimming or exercise. Unused natural insect repellent may be stored in a dark bottle, away from heat or sunlight.
If you are making large amounts of mosquito repellent, a good rule of thumb is to mix the repellent so it’s 5-10% essential oil, so mix 1 part essential oil with 10-20 parts carrier oil or alcohol.
For a smaller batch use:
10-25 drops (total) of essential oils
2 tablespoons of a carrier oil or alcohol