Silicones smother hair, making it impossible for your strands to absorb proper moisture. Just like your body, when adequate moisture isn't available, your hair becomes dehydrated and, coupled with the buildup of chemicals ... SNAP! The hair that once looked so lush and shiny starts to break.
The scalp has also been stripped of its natural oils from harsh foaming agents like sulfates and is no longer responding to the synthetic softeners for replenishment.