Consumer Council says more than half of samples tested positive for 1,4-dioxane, an ether US authorities say could affect the liver and kidneys in the long term

Hong Kong’s consumer watchdog has found 38 out of 60 shampoo samples it tested contained a harmful solvent used in manufacturing, with seven exceeding the limit recommended by the European Union.

The Consumer Council also found 20 per cent of the shampoos contained allergy-causing preservatives, and one even tested positive for a heavy metal.

But the agency insisted none of the samples constituted an “immediate” health risk, and only urged those with sensitive skin to be extra cautious when making their choices.

A total of 60 shampoos available in Hong Kong were collected for examination. Most were general shampoos not targeting specific hair problems or types, but some claimed to alleviate hair loss.

Revealing the test results at their monthly briefing on Tuesday, the council said 38 contained 1,4-dioxane, an ether commonly used as a solvent in manufacturing.

The contaminant is often found in cosmetics, detergents and shampoos, but the United States Agency for Toxic Substances and Disease Registry suggests long-term contact of the liquid form with the skin may affect the liver and kidneys.

While the concentrations of 1,4-dioxane in the samples all fell within mainland China’s limit of 30 parts per million, seven shampoos exceeded the European Union’s ceiling of 10ppm.

They included products by Head and Shoulders, Clairol, Pantene and Vidal Sassoon.

In response, these brands said 1,4-dioxane was “inevitably” produced “in trace amounts” during the manufacturing process, but the products remained safe to use.

Council chief executive Gilly Wong Fung-han also urged consumers not to be too worried if using these shampoos under normal circumstances.

“But if you have a sensitive scalp or skin, or experience allergies when using the products, then you should take extra caution or even consult a doctor,” she said.

Asked whether consumers should avoid products with 1,4-dioxane altogether, Wong said it was up to the individual to decide.

“Thirty-eight contain 1,4-dioxane, while 22 do not,” she said. “We are offering people an informed choice.”

Also detected in 12 samples were the preservatives methylisothiazolinone (MIT) and methylchloroisothiazolinone (CMIT), which are often added to personal care products to inhibit bacteria growth.

One sample, Head and Shoulders Silky Soft Anti-dandruff Shampoo, even contained 0.18ppm of the heavy metal arsenic, although that was below China’s limit of 2ppm.

Dermatologist Kingsley Chan Hau-ngai said that while a serious allergic reaction was unlikely to occur from using the shampoos tested, due to the relatively short time they stayed on the skin, they could still cause irritation, especially in open wounds.

Wong Kam-fai, who heads the council’s research and testing committee, said everyday shampoos containing silicone only added a temporary smooth and glossy finish to hair but would not repair damage.

He also warned shoppers that shampoos said to be “mild” or made with natural ingredients were not necessarily free of harmful substances, and consumers should scrutinise labels on bottles before buying.