Why do nurses wearing White caps?

I share the opinion of owlwings, that the nurse hat is to keep their hair intact so that it does not fall on the patient. White symbolises anything that is clean and it helps to show that the nurses are a clean creature.

People who work in environments where cleanliness is essential often wear white because any speck of dirt can easily be seen. It is not so much symbolic as practical. Those who work in operating theatres generally wear green because it is the opposite colour to blood and any blood on their overalls can easily be seen. Butchers, chemists and many other professions also commonly wear white overalls. The wearing of caps is also practical. It is designed to keep the hair in place and to stop any hairs or anything else from the head falling on the patient. People involved in food preparation also wear caps or hats for the same reason and the tall, white chef's hat is designed to act like a chimney to draw heat away from the head and to absorb sweat (because working over a stove is a very warm occupation).