Another basic variation of repellents is between natural and synthetic. These titles speak of the active principle in their formulas, i.e., the substance that actually repels mosquitoes.
The natural ones are made of plants, especially citronella and eucalyptus, and for this reason are safer as to the body's skin reaction. On the other hand, they have a less lasting action, from two hours down.
The synthetic ones are usually made based on one of these three substances, DEET, IR 3535 and Icaridin, which must have their concentrations controlled, but which act for a longer time after each application.