Used in Chinese medicine for centuries to aid a raft of ailments, fresh aconite is extremely toxic, and safe dosage is dependent on processing. Many species are used medicinally in China only after extensive preparation.
A man in his 50s a woman in her 30s both remain in hospital in San Franciso after experiencing life-threatening, abnormal heart rhythms.
"This aconite poisoning which can come from Chinese herbal teas if not processed correctly it can affect the heart. It can give them neurological symptoms like tingling it can also give you nausea and vomiting," said Dr Tomas Aragon, health officer for the city and county of San Francisco.
The tea leaves were bought from Sun Wing Wo Trading Company.