Magnets are used in computer data storage, compasses, doorbells and alarm systems, microphones and speakers, motors, electrical generators and electrical transformers. They are also used to levitate objects, including trains that operate via magnetic propulsion. Naturally occurring magnetism protects the Earth from cosmic radiation.
Magnets are also used in a variety of medical and veterinary applications. Magnetic resonance imaging uses magnetic fields to view internal organs, and electromagnetic fields promote the healing of broken bones. A similar treatment prevents bone loss in astronauts outside of Earth's gravity.
In veterinary medicine, magnets are used to treat hardware disease in cows. The condition occurs when cows swallow metal objects, which can puncture their organs. Cows can be fed magnets as a preventative; any metal objects swallowed will be drawn to the magnet instead of puncturing the cow's stomach. Magnets can also be used to ensure cows' feed is clear of metal objects before ingestion. Unlike in cows, swallowing magnets is a medical emergency for humans; they can perforate the intestines.
Other medical uses for magnets, such as applying magnets topically to treat pain, are not proven by scientific studies. Magnetized drinking water is similarly unproven; scientific studies show no evidence that it has any health benefits.