What Causes Red Patches On Ankle Followed By Swelling?

2Days ago I notcied that I had a red patch on my left ankle and 3smaller ones on my right top foot and knee. The it hurt to walk my left foot got really swollen and then got a bigger red circl around the patch. Today swelling has gone down but the red patchs are turning a deep color. Also have buch of red dots on both legs.