What Causes Itching Sensation All Over Body Post Hernia Surgery?

HI,I have itching problems on hole body area, not in hernia repaired area, and it started after one year after surgery. I did all allergy tests, and it results without any other allergy cause like food, polen etc. As I see, on this page, other people have the same problem. So it is very strange that other patients feel the same. I doubt it is coincidence. So I think that medicine workers should it consider seriously.Best regards