How To Cure Itchiness All Over The Body?

i have ichy skin all over my body, it also has a very mild chill affect on my body when i get it, i have been tested for liver and thyroid and they they came out neg, however my kydneys came out a little high, nothing to worry about the doc said tho. i know its not food coz i have monitored with a food diary, what could it be im very worried about it coz when its ichy its seriously ichy and loads of bumps appear on my chest and hands mainy.