I Often Have Swelling In Different Parts Of My Body.

I often have swelling in different parts of my body. Today my for arm is red, hot swollen, and sometimes it itches. The top of my foot, my thumb, even the side of my stomach was swollen at one point. I have been to the doctor and had blood test run, but no one knows what is happening. It is painful as well. I have tested for gout and my test was negative. I'm concerned and need some help figuring this out. It happens on a weekly bases, then it goes away only to return in a different part of my body. Mostly it is the top of my foot and toes, and my arms, and thumbs.