Banlangen granules are a combination of several herbs, which should be taken under medical guidance. Liu Jiao / For China Daily

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."

Only a TCM practitioner can decide if banlangen is suitable for treating an ailment, Zhang insists, and if not the undesirable side effects can include discomfort to the digestive tract, especially children and the elderly.

In some extreme cases, banlangen may cause diarrhea and dehydration, Zhang warns.

"Additionally, it is nonsense to suggest that banlangen can boost the immune system. And if there is no disease, why bother to take medicines? It is like fighting an enemy that exists only in the imagination."

Ke Huixing, vice-director of the respiratory diseases department at Beijing Hospital, says: "To date there have been no clinical trials or observations confirming the efficacy of banlangen against the H7N9 virus."

Therefore, Ke suggests, people should not take the herb, unless directed to do so by a qualified TCM practitioner.

Doing so could affect the metabolism, including the digestive tract, kidney and liver. It will do more harm than good to take banlangen to prevent H7N9 bird flu infection if someone is healthy, Ke confirms.

"The government and experts should take responsibility to explain to the public that there is no need to panic."

Instead, Ke says people should keep fit to maintain their immune systems and be careful not to come into contact with infected poultry.