The Department of Health urges the public not to use a product called "Tai Er Si Yi Wei A Suan Jiao Wan" which claimed to contain a Western ingredient, isotretinoin, that may cause serious side effects.

The product, on sale at an internet auction site, is not a registered pharmaceutical product in Hong Kong.

Taken orally, isotretinoin is used for treating severe acne and is not indicated for uncomplicated adolescent acne.

Isotretinoin's common side effects include dryness of skin with scaling and redness, conjunctivitis, dry sore mouth, visual disturbance, hair thinning and mood changes.

It may cause foetal malformation and spontaneous abortion and should not be used during pregnancy. Pregnancy should be avoided for one month after the treatment has been stopped.