|MadSci Network: Microbiology|
We did this when I was an undergraduate. The simple thing to do is to is to wash your hands with the different soaps and loations and see how many bacteria are left afterwards. So what you do is wash your hands with the soap thoroughly and then stick your fingers on the petri plate and see how much grows after you wash your hands.
The problem is how to be consistent. For science fair you are going to need to be able to say that your hands were equally covered with bacteria each time. This is hard to do, so what I would do is do each soap or lotion two times and show that the result was the same both times.
A good control, that usually kills everything, is 100% alcohol, or rubbing alcohol, you gan buy this at the pharmacy usually. If you wash your hands good with the ethanol there should be nothing left.
Be prepared alot of them DON'T work. Hint: I think I remember that Dial antibacterial is particularly bacteria friendly.
Also don't use soap fresh from the wrapper. When is the last time you used soap fresh from the wrapper. Use the one that the whole family uses, let them use it for four or five days and then see how antibacterial it is. It makes a big difference, you can even do that to compare washing your hands with a fresh bar a soap and with the one that everyone has been using in the shower for the past week.
Also compare the amount of time you wash your hands for. Sya 10s, 30s, 60s.
Try the links in the MadSci Library for more information on Microbiology.