Banlangen granules are a combination of several herbs, which should be taken under medical guidance. LIU JIAO / FOR CHINA DAILY

"Although banlangen does function as an antiviral, it has side effects and may cause allergic reactions," says Zhang Wei, a TCM expert in Shanghai.

Traditional Chinese medicine should be used under medical guidance and if not can have negative effects, he adds.

"Banlangen granules are a combination of several herbs," says Zhang Shunan, vice-director of the lung diseases department at China-Japan Friendship Hospital, a TCM practitioner, and executive director with the World Federation of Chinese Medicine Societies.

"It is a staple traditional Chinese medicine that has been used for colds and other ailments for ages, but it cannot be used as a universal preventive drug against the new bird flu."

Firstly, he says, there is no such thing as a TCM preventative prescription that works for everyone. This goes against the key doctrine of TCM that emphasizes personalized prescriptions for each individual, according to their situation.

Second, there are different types of colds and flus that are variously categorized as "cold-natured" and "heat-natured".

Banlangen only can relieve the symptoms caused by heat-natured diseases, Zhang says. "You can't simply say banlangen does or doesn't work against bird flu."

"Whether the herb can treat the disease or not is dependent on whether the disease is heat-nature based. It is not about the disease alone, it is related to the symptoms that are determined by the disease, the patient's physical condition, the environment and the weather, taken as a whole.

"If the patient's symptoms are caused by a bird flu that has a heat nature, banlangen can treat the disease, otherwise, it cannot."