Extremely itchy on legs and sometimes other part of my body?

Sometimes I get extremely itchy. Most of thee time it's on my leg above my knee and under my knee. The area of my body gets really hot and then turns red. I'm guessing that's from scratching because it goes away but tiny little bumps also form where ever I am scratching. They also go away but I don't know what they are. I changed soap and whenever it happens I try to take a shower and move around a lot and it mostly goes away. Sometimes it also occurs on different areas of body including my stomach and back. Anyone have any ideas?

 

Stop eating sugar. I would have incredibly itchy skin which became REALLY agrivated during the winter months where i would have gladly taken a knife to my back to cut the itch off. It didnt go away until I stopped eating all sugar and comes back if I do.