Mercury is a very strong inhibitor on melanin synthesis. Unfortunately it is also highly toxic when excessive amount is absorbed. In the past it had been widely used in fading freckles and other pigmentary problems.

There are still some anti-freckles creams on the market, mainly those manufactured in Mainland China and Taiwan, contain high levels of Mercury but do not show it on the labels.

The US FDA limit of Mercury content is 1ug/g. An analysis of 38 brands of cosmetics cream available in Hong Kong revealed 8 (21%) exceeded this limit. All these high-Mercury brands are manufactured in Mainland China or Taiwan.

Symptoms of Mercury intoxication are essentially non-specific and include tiredness, back pain, headache, nausea. Less frequently there is frothy urine, diarrhoea, double vision, articulation difficulty, walking imbalance, and twitching.

It is strongly recommended not to use any bleaching cream that does not have a clear labeling of its contents. Awareness of the problems and high degree of suspicion are very important in aiding the diagnosis.