I've spent a lot of time staffing summer camps in Louisiana, Missouri, and now New Mexico. Of course, we don't have the bug problem in the New Mexico mountains.
Vitamin B1 with Thiamine (sp?) works much like a garlic tablet would by emmitting a slight odor through the skin. However, unlike garlic tablets, this odor is not offensive to humans. It does take a couple of weeks of daily intake to build this up in your system. Also, you need to take a specific B1 tablet; a multi-vitamin or B complex won't work.
This has worked for me for over ten years. If I know I'm going to be in an area where the bugs are unusually thick, I do add some reppellant.
Avoiding perfumes and heavily scented soaps will also help keep the bugs at bay. Also remember that some bugs are attracted to the salt on the skin - from the ocean or from perspiration.