In all properly controlled experiments that have studied it, vitamin B1 has failed to have any effect on pest landing, probing, or biting rates. In fact, despite extensive searches, no food, supplement, or drug of any kind has ever been shown to make anyone repel any insects. The explanations for why vitamin B1 fails to repel mosquitoes are numerous, starting with the fact that vitamin B1 is nutritious for mosquitoes too, so there is no reason they would fear it. (Photo by Matan Shelomi, Ph.D.)