|OTC treatments such as Tecnu and Zanfel work by removing the urushiol oil from the skin. OTC treatments such as Calamine lotion work by helping to sooth the skin.
I'm a bit surprised that the Calamine didn't work to help alleviate at least some of the itch. One thing to keep in mind that stress (like fretting over the itch) causes a release of histamines - that means more rashes and more itching. So how about trying a treatment that could also be quite soothing. Have you tried an oatmeal bath? Many swear by this treatment.