It has been said that cleanliness is next to godliness and perhaps it is true or maybe it's an exaggeration. There is no doubt that being physically free of dirt and germs has many advantages and at the top of the list is the impact on one's health. Dirt and germs can cause infection of various kinds and one of the easiest things that can be done to keep sickness and infection away is to keep the body clean. Now when it comes to staying clean there are many modern conveniences which help. Near the top of the list is soap. Not only does soap and water help wash away dirt, but viruses and bacteria are actually killed as a result of sufficient exposure to soap. The key concept here is "sufficient exposure" and as a general rule it is estimated that it takes twenty seconds of vigorous hand washing to render the hands free of germs. In fact, many people sing the "Happy Birthday" song to themselves as they wash their hands since the duration of the song is approximately twenty seconds.