What Causes Red Itchy Spots On Hands And Legs?

A couple of nights ago, I woke up during the night with an intense itching along the elbow and going up the underside of my arm. It really itched bad and I thought perhaps something had bitten me, but my husband never has any problems. I couldn't go back to sleep as it continued to itch. I looked in the mirror and there were 3 or 4 red knots. The next day, they continued to itch and I used 1% hydrocortisone spray to help relieve some of the itching. They are still there, but don't itch quite as much as before and seem to have gone down some. After thinking about it, this happens to me once or twice a year. A few days before that, I woke up one morning with a red spot on my leg just below the knee that was a bit larger than a silver dollar. That part of my leg felt stiff and the spot felt warm. There was a tiny pimple in the middle of it. I put a washcloth on it that I had wet with water as hot as I could stand it and it seemed to feel better. The little pimple also itched a lot. After about 2 days, it went away. Could tthis be some kind of allergy? I did have eczema as a child and still have a small spot on my index finger that refuses to go away. Help please...