Croton oil (Crotonis Oleum) is an oil prepared from the seeds of Croton tiglium, a tree belonging to the natural order Euphorbiales and family Euphorbiaceae, and native or cultivated in India and the Malay Archipelago. Small doses taken internally cause diarrhea. Externally, the oil can cause irritation and swelling. In traditional Chinese medicine it is used as an ingredient in some liniments.
Croton oil is the source of the organic compound phorbol.Today croton oil is the basis of rejuvenating chemical peels, due to the caustic exfoliating effects it has on the dermal components of the skin. Used in conjunction with phenol solutions, it results in an intense reaction which leads to initial skin sloughing and then eventual regeneration.
Since croton oil is very irritating and painful, it is used in laboratory animals to study how pain works, pain-relieving and anti-inflammatory drugs, and immunology.
During World War II, the United States Navy added a small amount of croton oil to the neutral grain spirits which powered torpedoes. The oil was intended to prevent sailors from drinking the alcohol fuel. Sailors devised crude stills to separate the alcohol from the croton oil, as alcohol evaporates at a lower temperature than croton oil.
Croton oil is also more effective for production of biodiesel than Jatropha. One can obtain 0.35 litres of biofuel from a kilo of croton nuts.