Organic mosquito control sprays generally contain essential oils, which are distasteful to mosquitoes, and carrier oil or alcohol as ingredients. Some of the essential oils that repel mosquitoes include cinnamon oil, lemon eucalyptus oil, citronella oil and castor oil. Carrier oils that may be used are olive oil, sunflower oil and other vegetable oils. One part essential oil is typically mixed with 10 to 20 parts carrier oil or alcohol.
As of 2014, the US Department of Agriculture ranks Repel Lemon Eucalyptus Repellent as the best natural mosquito repellent available commercially that is DEET-free. Next to Repel in effectiveness is Bite Blocker, which is made of geranium, soybean and coconut oils. Lotions, sprays and candles made with citronella oil can also help protect against mosquito bites but should be used in combination with other topical repellents for complete protection.
Other promising ingredients for organic mosquito repellents include fennel oil, thyme oil, clove oil, celery extract and neem oil. Two compounds, carvacrol and alpha-terpinene, which are derived from thyme oil, have been found more effective than commercial repellents with DEET. However, homemade mosquito repellents containing thyme oil or clove oil may cause skin irritations. Neem oil contains azadirachtin, an insecticidal compound with mosquito-repellent properties.