Black, scissors are my primary cutting 'tool', and mine does the same thing everything... Not even 5 seconds after cutting, it swells up around it. It's not that it's infected, it's the fact that your skin has just been traumatized and your skin naturally swells when it's wounded. Scissors usually take a bit more effort and time to cut the skin open, so you're repeatedly slashing across the same spot unstead of just a slash and it's an open wound like with a razor blade. That's why the scissors leave a swelling effect. I'd only be concerned with infection if the swelling last more than 2 days, by then the swelling should be gone and it should just be a wound healing. I'm not encouraging you to cut, but please, everytime you get the urge and give in to that urge, make sure you put fire (from a lighter, etc) to the scissors for a few seconds to sanatize it, because that will lead to infection if you don't.