We do backpacking in remote areas in northern Michigan where mosquitoes and black flies can make a trip unbearable. I read about taking Vitamin B6 to prevent bites, tried it and found it completely successful. But one time when backpacking with our daughter, I had forgotten the B6 but was taking Vitamin C up to my bowel tolerance level for a specific medical problem. So my blood and cells were full of Vitamin C. I noticed that my daughter's legs were covered with mosquitoes and black flies and in a few minutes, each bite would swell up and become red. I was surrounded by flies and mosquitoes but either I was not bitten (I did not feel anything) or I did not have any reaction. I think that the mosquitoes do not like the high acid content of the blood (I was taking the acidic form of Vitamin C). In addition, when cell and tissue fluid are saturated with Vitamin C, edemas will be removed by the body very quickly. I think this probably is why bites either do not swell or do not last very long if people are taking Vitamin C.