What Causes Feet Soreness, Swelling And Tingling Pain With Discoloration?

Hi, this has happened before but not with the pain but whilst i was abroad my feet started feeling sore, then both feet swelled up so my ankles werent visable. Later on that night i had very painful pins and needles/ numbness on my feet and legs which then resulting in a very dark purple rash covering my feet and legs...any idea what this is? Ive had it twice before but never with the pain and ive just been given steriod tablets. Thanks