Peanut oil

Peanut oil, also known as groundnut oil or arachis oil, is a vegetable oil derived from peanuts. The oil usually has a mild or neutral flavor but, if made with roasted peanuts, has a stronger peanut flavor and aroma. It is often used in American, Chinese, Indian, African and Southeast Asian cuisine, both for general cooking, and in the case of roasted oil, for added flavor.
History.
Due to war shortages of other oils, use of readily available peanut oil increased in the United States during World War II.
Uses.
Unrefined peanut oil has a smoke point of 320°F/160°C and is used as a flavorant for dishes akin to sesame oil. The refined peanut oil has a smoke point of 450 °F/232 °C is commonly used for frying volume batches of foods like French fries.
Other uses.
Peanut oil, as with other vegetable oils, can be used to make soap by the process of saponification. Peanut oil is safe for use as a massage oil.
Biodiesel.
At the 1900 Paris Exhibition, the Otto Company, at the request of the French Government, demonstrated that peanut oil could be used as a source of fuel for the diesel engine; this was one of the earliest demonstrations of biodiesel technology.
Composition.
Its major component fatty acids are oleic acid (46.8% as olein), linoleic acid (33.4% as linolein), and palmitic acid (10.0% as palmitin). The oil also contains some stearic acid, arachidic acid, behenic acid, lignoceric acid and other fatty acids.
Nutritional content.
Peanut oil is 17% saturated fat, 46% monounsaturated fat, and 32% polyunsaturated fat (table).
Health issues.
Toxins.
Highly refined peanut oil can contain traces of hexane, a petroleum byproduct used to maximize separation of oil from the solids of peanuts. The EPA identifies hexane as a neurotoxin in rat studies. There are no specific regulations on the limits of hexane use in cooking oils. If quality control is neglected, peanuts that contain the mold that produces highly toxic aflatoxin can end up contaminating the oil derived from them.
Allergens.
Those allergic to peanuts can consume highly refined peanut oil, but should avoid first-press, organic oil. Most highly refined peanut oils remove the peanut allergens and have been shown to be safe for "the vast majority of peanut-allergic individuals". However, cold-pressed peanut oils may not remove the allergens and thus could be highly dangerous to people with peanut allergy. 
Since the degree of processing for any particular product is often unclear, "avoidance is prudent."