As a kid, I lived in Florida. During survival merit badge training class, we had an old Florida "Cracker" come and lecture about swamp survival. We were all sitting around and getting bit badly by mosquitoes, and he wasn't. We asked why...
He said stop eating bananas. He claimed the banana oil secreted through your skin via sweat attracted them like nothing else could. He said it would take a year or more to fully work and get the banana oil out of your system. Not being a fan of bananas, I stopped eating them, and never went back.
Fast forward almost 35 years, and now, each summer, I am the one not being bitten, right amongst a crowd of people being devoured by bites. No kidding. I have sat outside between my wife and adult child - (both whom say the Florida "Cracker" was a crackpot) while they are being bitten - even on occasions when they applied Deep Woods Off! - while I am not bitten, with no repellent on at all.
I swear by it, but you do lose a great source of fiber and potassium. I take a vitamin anyway, and enjoy other high fiber foods.
Take his story with a grain of salt, but it has worked for me.