You may want to google "Vitamin B insect repellant".
Virtually all of the professional organizations, university studies, health agencies etc.. Say there is nothing at all to suggest Vitamin B will act as a repellant, and the majority of those claiming how good it is are from someone selling it. Think about it.
Your asking about this as a mosquito repellant to be used in an area that has mosquitoes that carry serious diseases, Of course it's up to you and you only but I will stick with the most often recommended product, which I know works well for me for both mosquitoes and sand flies.
I am interested in How these can even legally be called and insect repellant in the US when it has not gone through the proper testing. That is why on Roatan the famous cactus juice has a sticker on it calling it a repellant yet on US shelves it does not.