I too have had bad luck.. so far ive got a plantars wart, molluscum contagiosum rash on my arm which lasted for almost a year, ring worm, eczema, and now some weird rash on my knee. But ive gotten it all treated with the help of a good dermatologist.
Ive learned my lessons the hard way..
Always wash your GI after every class.
Wear a long sleeve rash guard every time you roll.
Before class, inspect yourself for any open cuts/wounds. Clean them and cover them completely before training. Note: when training, you will be sweating so make sure the bandage is on firmly.
Shower immediately after class, preferably with some anti-bacterial soap. (
www.defensesoap.com) and clean/disinfect/cover any new cuts/wounds you may have obtained.
Try not to roll with someone who has a rash or something weird on their skin, also avoid people who do not wash there GI's every-time.
Lastly, even when taking these precautions you may still have something crop up, make sure you have the number of a good dermatologist ready. If you see something that looks a bit weird, get it checked out early, it will avoid a lot of hassle in the end, believe me.