I have been getting a strange red rash, inflamation on my arms and the tops of my hands that will flare up in the evening, but than disappear in the day. What could this be?

It is itchy, but not unbearable. I seem to figure out why this keeps appearing or what it is from. The rash is red inflamed blotches not small bumps. They start on the tops of my hands and will go up the forears and them a little on the upper part of my arm, just below my shoulder.