Bad press, however, hasn't affected Airborne's business. Last year it was the market leader in the US$250 million immune health sector in the US. In Hong Kong, health products chain Nature's Village sells five to six different types of Airborne supplements nearly every day. 'It's popular,' says Aman Dhillion, store manager for the Lyndhurst Terrace outlet. 'People come to our store looking for it.'

It seems, however, that yin chiao isn't quite the cold remedy you expect it to be.

According to Dr Liong Ching, an instructor at Chinese University's School of Chinese Medicine, 'cold syndrome' is associated with white secretions, a runny nose, chills, lethargy and a slow pulse, and that requires a completely different prescription.

Yin chiao is a very popular powder prescribed to patients for febrile disharmony or 'hot syndrome', a common summer ailment. The concoction contains honeysuckle flower, St John's wort, hairy sage, fermented soybean, balloon flower, mint, burdock, liquorice root and bamboo leaf.

Febrile disharmony is associated with feeling hot and feverish, having a rapid pulse, sweating and having a sore throat. 'It is very common in Hong Kong, but not so much in the north. Yin chiao is not preventive for colds and flu and is traditionally prescribed to relieve only symptoms indicative of heat,' says Liong.

Many other over-the-counter products are touted as updated TCM remedies, but the way they are marketed in the West may not always agree with what the Chinese experts say.

Gingko biloba is one example. With worldwide sales worth hundreds of millions of dollars each year, it is a modern-day TCM best-seller billed as being able to boost brainpower.

But Liong says: 'The brain enhancement functionality of gingko biloba is not present in ancient Chinese literature. In fact, in the Pharmacopoeia of the People's Republic of China 2005, considered the most authoritative compendium for all aspects of TCM, the therapeutic effect of ginkgo biloba is not listed as a brain enhancer. It's used for excessive coughing or excessive secretions, especially related to women.

'I really don't disagree or agree with the product being used as an enhancer for the brain or memory, but I would never prescribe it as such.'

What about dong quai, also known as Chinese Angelica, which has been used for thousands of years in TCM for women's health issues?

It has seen a recent resurgence in popularity, being sold as a stand-alone herbal remedy worldwide to help support hormonal balance and maintain healthy oestrogen and progesterone levels in women.

Liong, like many Western gynaecologists, has her concerns. 'I don't know any TCM specialist who would prescribe dong quai as a herbal remedy on its own,' she says. 'It must be used in a formula.' That formula is: Chinese angelica, Sichuan lovage, Chinese foxglove and white peony root.

According to the Pharmacopoeia, it is this herbal combination that promotes regulation and well-being before, during and after menstruation.

Prescribed to promote qi (the vital energy that flows through all living things), the formula revitalises blood flow that often gets stuck during premenstrual syndrome, thereby averting symptoms such as swelling, abdominal pain, fatigue, cold limbs and lower back soreness.

According to Memorial Sloan-Kettering Hospital, dong quai has shown to increase the growth of breast cancer cells in lab tests, and may also contain compounds that can cause cancer in high doses. However, Liong believes that dong quai's potency is modified when prescribed in the traditional formula. A believer in its therapeutic effect, she still prescribes it.