Jamaican vomiting sickness is an acute illness caused by the toxin hypoglycin A, which is present in unripened fruit of the ackee tree. Hypoglycin A is present in the unripe arilli at levels of over 1000 ppm, which falls to less than 0.1 ppm in the fully ripened arilli. Hypoglycin B, found only in the inedible seed, is believed to be a derivative of hypoglycin A. Its concentration rises from 0.4 mg/g to 3.3 mg/g as the fruit ripens.