Several home remedies have been used to try to repel mosquitoes, including eating garlic, vitamin B12 supplements and applying herbal essential oils. Several university and research centres have tested vitamin B12 supplements for their efficacy.
The University of Florida IFAS Extension found no scientific evidence to support the use of vitamin B supplements, including B12, as an effective mosquito repellent. The University of Wisconsin's Integrated Mosquito Management program reached the same conclusion.
Mosquitoes are enticed to bite due to a complex interaction of visual and chemical cues. The University of Florida IFAS Extension admits that some foods or vitamins may increase or decrease a given individual's attractiveness to mosquitoes, but the reasons why they may affect one person in one way and another in the opposite way is not understood. However, vitamin B supplements do not provide the kind of consistent results necessary to earn an endorsement as an effective mosquito repellent.
Vitamin B does seem to help ward off another biting bug related to the mosquito: the flea. Vet Info says dog owners have experienced some success in warding off fleas by giving their dogs vitamin B and garlic supplements.