One day my lower leg was very itchy I looked at it at there was a load of small blister. The itch was bad so I put a plaster on it. I left it a few days and took the plaster off and the little blisters were gone but the area was still very red. After 6 weeks the itch came back later on I could feel my leg was wet, I looked down and there was a huge blister full of fluid. The fluid drained out and my leg is still itchy. I put a plaster on it to stop itching it. What could it be, I don't recall ever anything happening there?

Sounds like an allergic reaction to something... usually its something like poison Ivy or Poison Oak, but it could literally be anything including your laundry detergent, particularly if you started using a different one recently.