Cashmere is delicate material designed with unique propositions which allow them to be washable. Most of the cashmere sweaters are tagged with a guideline which suggest you can dry clean or wash it manually by bare hands. You can either use baby shampoo or Wool and cashmere shampoo (nontoxic and mild detergents) to clean them. The stain solution can be applied directly on collar and underarm to get rid of stains which are precisely formulated. To sustain your cashmere for a long time, its best to wash them with cold water, soak for 30 minutes and rinse it preventing them from shrinking and color fading.
NOTE: While dry-cleaning, you must determine adequate temperature, cycle and detergents to prevent them from damage.