What Causes Rashes Below Penis Foreskin?

Hi, I am advised by my Doctor to take VDM kit as I have some rashes and white paste like substance below my penis foreskin. This happens once in 1-2 years. Is it safe to use VDM kit and my wife also has been asked to use this as well. I am diabetic and take glymy MP1 one tablet daily. My wife is normal. Please advise,