Vitamin B-12 wards off ticks, fleas, chiggers, and mosquitos. If you take an excess you’ll sweat it out, which masks the smell of your blood. Unfortunately it doesn’t work on bedbugs.
I have no other explanation of how us kids managed to play in tall grass and woods all the time, and never get bug bites. We picked up the occasional tick, but it was the dogs that the insects went after, not us.
It's so peaceful (startrek.website)