What could cause a chronic rash?

What could be the cause of this rash?

• Yesterday, I noticed a rash on my knees. It's red, blotchy, and a bit raised from the non-irritated skin. It isn't itchy. I've never gotten this before, and I'm not sure what it could be from. My only thought is that yesterday, I shaved my legs in the shower. I realized later that I mostly missed my knees (I wasn't paying attention). I didn't feel like getting back in the shower, so I just wet the razor blade, and shaved my knees, without shaving cream as well. The blades on the razor aren't dull, I've only shaved a few times since I last changed the cartridge. The reason I think that the rash could be because of the shaving is because it showed up after I shaved (not immediately though), and the rash is only on my knees.Does anyone know what this could be from? Luckily I'm going to the doctor's tomorrow anyways, so I can ask then, but I'm still curious to know now.

• Answer:

  razor burn. rub on some gentle moisturizing lotion. it'll go away in a few days.