The Consumer Council yesterday warned people who use 'progressive' hair dyes that gradually colour their hair black to be wary of damaging chemicals.
Tests by the council showed that five out of eight samples contained lead acetate and silver nitrite that surpassed internationally accepted safety levels.
These chemicals may damage the nervous system and eyes after excessive exposure.
'Try to pick products with the least amount of lead acetate and silver nitrite and if possible avoid usage,' said Ching Pak-chung, vice-chairman of the publicity and community relations committee of the Consumer Council.
Three of the five samples were found to contain more than 1 per cent of lead acetate, which could damage the nervous system, red blood cells and kidneys after excessive exposure. It could also cause permanent brain damage if the condition was not treated.
The products included Red Peach Darkening Hair Cream, Royal Concubine Hair-Restoring Cream and Guihua Hair Restoring Cream.