Ummm....I would think that most mouthpieces/carts made of similar material, so if you are alergic to one, most likely you will allergic to the other as well. But, a texture surface material is an invitation for bacteria build up compare to a smoother surface. But, that doesn't mean a smoother surface material won't get bacteria build up. Maybe, you are allergic to bacteria build up?. Have you try leaving your mouthpieces/carts in alcohol to disinfect it every other day to see if it will help?, and change or wash your cart's filling?. (leave it air dry for 24hrs for the alcohol to evaporate before you use it again).
I disinfect my e-cig frequently, including the atomizer, except for the batteries. As most will find out that if you dip the battery in any liquid, that will surely ruin your battery. I use a toothbrush and dap a little bit of alcohol to brush around the thread area of the battery. Cause sometimes, e-liquid can leak and get down to the battery's threading area.
Just curious, what kind of allergy symptoms do you have?.