I've never had a problem with the Mach 3 cartridges, though don't use 'em too many times -- more than a week or two -- that's when I have razor burn problems is when the blades are getting dull. I also tested the 5-blade Gillette Fusion before it was marketed and had no problems with that, either. I use the razors on everything: face, back, chest, groin, etc.