The inside of the elbow is some of the most sensitive skin on the body (even more sensitive than the face!) and tends to have more "violent" reactions to even the slightest amount of agitation. You could be developing a sensitivity to something in the bar, or something the bar touched, or something you touched before you touched the bar etc etc. Cocoa butter and shea butter are definitely things that you can become sensitized to over time (not sure about the other oils!). It could also be from something else all together and just be coincidence that you put the lotion bar on there at that time. The "inner elbow" is know for contact dermatitis (itchy red rash, usually with bumps, and sometimes a deep burning sensation). I have a bad spot there myself, from my own sweat of all things! Try some hydrocortizone cream to clear it up (the 1% "eczema cream" in the purple and red tube works great! I forget the company name though)!