I used the Free & Sensitive Downy. When it's all in the pan, it smells faintly, but on the doll- it had no effect.

I also washed my doll's hair and conditioned it with American Girl's real beauty shampoo/conditioner. (Which, by the way, is lovely smelly. Apparently the "creamy" in "creamy vanilla" is jasmine.) I'd never washed a doll's hair before, but she turned out fabulously.