Re: When is Naruto gonna stop molding chalkra? Or Charkra?
The damage only occurred when he first tried it (he didn't throw it). Now that he can throw it he doesn't have to forcibly push the rasenshuriken into his enemy which breaks down the cells in his hand. Also, it's spelled "chakra".
Edit: Kyuubi mode and Sage mode have little-to-nothing to do with Rasenshurikens cell-destroying abilities.