Croton oil 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 that 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.