Petroleum jelly is a mixture of hydrocarbons which is semisolid at room temperature, and it is also odorless, when properly refined. It is used in a variety of industries, although many people associate it with the popular Vaseline® brand personal care product. It may also be marketed as petrolatum or soft paraffin. Many general stores carry petroleum jelly, and it can also be found at medical supply houses and drugstores.

In 1859, workers on oil rigs noticed that a dense substance was clogging their drills. Allegedly, someone came up with the idea of putting the substance on cuts and burns, and after some chemical refinement, commercial petroleum jelly began to be marketed on a wide scale. Initially, it was viewed as a cure-all, recommended for a wide range of medical conditions, although later analysis and studies suggested that petroleum jelly was not, in fact, a miracle cure. In addition to being used in personal care, petroleum jelly was also marketed for use as a lubricant, and it emerges in some surprising places sometimes.

In the sense of a personal care item, there are some practical uses for petroleum jelly. It does not heal cuts and burns, but it can keep wounds clean by sealing them off, which may be useful in emergencies. However, it can also trap infectious agents under the skin, and it should never be used on fresh burns. As a skin protection tool, petroleum jelly can be highly useful, especially in cold weather, although it will leave skin feeling greasy.

Some people recommend petroleum jelly for chapped, runny noses, especially in the winter. Unfortunately, petroleum jelly should not be used around the nose, as it can cause a condition called lipid pneumonia, a lung infection caused by the inhalation of fats. It may also interfere with the nose's ability to naturally scrub air as you inhale, which could also contribute to lung infections. It should also not be used as a sexual lubricant in combination with latex barrier protection, as it can degrade the latex.

Petroleum jelly can also make a useful lubricant in some cases, although it can also gum up machinery. Because petroleum jelly protects objects from oxidation, it may be used to coat metals which are vulnerable to oxidation damage. Many printers and etchers, for example, use a thin coat of petroleum jelly to protect type and plates from oxidation so that they can be stored.