question: Hello doctor, I have a black patch on my back which is almost circular and is itching constantly. It has become quite big in the last three to four months. Can you please suggest what it could be and what I can do? It feels good when I put hot water on it. And it becomes very dry. It has a small line on its edges. The itching is happening continuously. It subsides a bit when I apply moisturizer. But the black patch seems to become darker.