Do they work? The short answer: yes, but some better than others. Plant-based insect repellents that contain oil of lemon eucalyptus do a better job protecting against mosquito bites than similar products made with citronella, cedar, or soybean oils, according to the CDC.
Additionally, studies show that lemon eucalyptus oil (look for p-menthane-3,8-diol on product labels) performs as well as chemical repellents with low concentrations of DEET. Of course, even natural products may have side effects. Allergic reactions to essential oils are rare but can occur. Oil of lemon eucalyptus should not be used on kids under 3. To find the right repellent for your area and outdoor activity, go to cfpub.epa.gov/oppref/insect/index.cfm.