What Causes Itchy Red Rash Below The Knee?

I have an itch and red skin down the front of my right leg. I coat it with aquafilic lotion each night. The redness has gone down because I try not to itch it. lt still continues to itch. I showed it to my doctor and she was just going to prescribe a hydrocortisone lotion. isn t that just treating the symptom and not the cause of this? It is only on one leg and I have had it since January of this year.