In most cases yes. The majority of natural repellents have studies behind them. In 2014, a comparative study was completed by using laboratory and field evaluations of repellent formulas containing DEET and lemon eucalyptus oil against mosquitoes in Queensland, Australia. This study found that the 40% DEET formulation provided 100% protection against mosquitoes for 7 hours, but the lemon eucalyptus oil at 32% provided more than 95% protection for 3 hours. So while DEET is found to be the most effective, there are plenty of natural ways you can repel mosquitoes.