Fingernails cannot be reattached after they fall off; however, they naturally grow back after approximately six months, according to WebMD. Nails can fall off due to several reasons, including skin conditions, fungal nail infections, severe illnesses and the use of chemicals such as acetone nail polish remover.
Home treatment for a detached nail involves removing any extra nail pieces, trimming the sharp edges and covering the exposed part of the nail with a non-adhesive bandage. WebMD recommends soaking the finger for 20 minutes in cold water and applying an antibiotic ointment. A torn fingernail can also be prevented by soaking the finger in salty warm water and applying an antibiotic ointment.