Croton oil (Crotonis oleum) is an oil prepared from the seeds of Croton tiglium, a tree belonging to the 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. Croton oil is used in Phenol-croton oil chemical peels for its caustic exfoliating effects it has on the skin. Used in conjunction with phenol solutions, it results in an intense reaction which leads to initial skin sloughing. 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. Because croton tiglium oil is cocarcinogenic, it has been used in tumor research. Croton oil is the source of the chemical compound phorbol. Tumor promotion activity was traced to phorbol esters present in croton oil. Pure phorbol 12-myristate 13-acetate which is found in croton oil is now used widely in laboratory research to induce tumor development. History 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. Norwegian partisans among workers at a factory, ordered by the Quisling government to turn over a catch of sardines to the Nazi German government for shipment to Saint-Nazaire (a U-boat base of operations) arranged with the British for a large shipment of croton oil to covertly poison the sardines, whose fishy taste was expected to conceal the tampering. In "The Bulletin" (9 Dowry Square, Hot Wells, May 29, 1845) by the Reverend Richard Harris Barham, a medically inspired poem to relieve the anxiety of a very dear friend, and written a month before Barham's death on June 17, 1845, the attending doctor to his patient advises amongst other treatments for a sore throat that is producing barely a sound: "... Please put out your tongue again! / Now the blister! / Ay, the blister! / Let your son, or else his sister, / Warm it well, then clap it here, sir, / All across from ear to ear, sir; / That suffices, / When it rises, / Snip it, sir, and then your throat on /