The present invention is directed to targeted delivery of a cold slurry underneath a patient's skin to improve the cosmetic appearance of the skin. The “target” tissue can be muscle tissue that when cooled cannot contract and cause wrinkles/lines in the skin to appear. The target tissue can also be adipose tissue that causes overlying tissue to sag and form wrinkles/lines. The cold slurry induces apoptosis, and reduces the size of the tissue, and causes the connective tissue supporting the skin to thicken and tighten, thereby reducing wrinkles/lines. Skin can also be tightened with cold slurry injected into the dermis layer of the skin or within the layers of the oral mucosa making a cold slurry treatment ideal for reducing the appearance of baggy skin after a patient loses weight and or for treating obstructive sleep apnea. Cold slurry can also be used to treat cellulite and acne.