Wavey,
I had the same problem not to long ago, I was on mezavant (5asa) and my liver enzymes were extremely elevated and my skin was soooo itchy.
I switched back to salofalk which I was on before for the last 17years and my skin is fine now.
Have you had bloodwork lately to see if it could be liver enzymes from the meds or disease itself.
ยป Mild to severe localized skin itching is another symptom which is quite common. Due to improper functioning of the liver, the toxins present in the body are no longer eliminated and they get accumulated in the skin and blood which gives a continuous itching sensation.
Read more at Buzzle: http://www.buzzle.com/articles/elevated-liver-enzymes-symptoms.html