What Causes Inflammation And Swelling In Hand?

The back of my right hand became red and swollen so the skin was tight and the veins were not visible. This happened without any trauma or bites that I know of. It has become less swollen over the last 2 days, the color is still red and tending to brown. No itching, scaling, moisture, or pain at the end of the 3rd day. However, the hand was feeling like it had been hurt the first day and then decreased until no pain at day 3.
The red discoloration stops abruptly at the sleeve line, almost like a reaction to some chemical happened.