Petroleum is a liquid crude oil that comes from beneath the earth's surface. In the past it was used in shipbuilding and road building and was burned as a fuel. Today, petroleum is one of the most important of the earth's resources for fuel. In orthodox medicine, petroleum was used to treat wounds, but it is only in homeopathy that it has become a widely used medicine. This remedy is mainly used to treat skin complaints, such as eczema, in which the skin is dry with deep, bloody cracks, especially on the hands and fingertips. The splitting of the skin is very bad in cold weather. It is also used for nausea, diarrhea, and vomiting, particularly when associated with motion sickness. Despite nausea and vomiting there may be constant hunger. People who require this remedy may have offensive smelling sweat and dislike fatty foods. They suffer indigestion from gas-inducing foods. Mentally, they may become excitable, quarrelsome, and confused.