The Consumer Council on Monday warned parents to be careful when choosing toothpaste for their children, after it found some products on sale in Hong Kong were too acidic.

The council examined 13 models of children’s toothpaste, and found that three of them – under the brands “Elmex", "Dr Brown's" and "Tom's" – had a pH level lower than the mainland standard, which may affect dental and oral health. A lower pH level indicates higher acidity.

"It is essential for the children to nurture the good habit of cleaning their teeth and oral cavity from a young age, in order to ensure the healthy growth of their teeth during the developmental stage. However, if the toothpaste's ingredients do not comply with the standards, it would affect dental and oral health despite good oral care habits," said Nora Tam, chairwoman of the council's research and testing committee.

She also advised parents to accompany their younger children when they are brushing their teeth, to prevent them from swallowing the toothpaste mistakenly.

Separately, the consumer watchdog reminded people to cut down on seaweed, saying most products are high in iodine and eating too much can cause thyroid problems.

The watchdog tested 27 seaweed samples and found that all of them contained a large amount of iodine.

In one product by "Baby Basic", the iodine level exceeded the recommended daily intake for toddlers by 90 percent.

Meanwhile, 70 percent of the seaweed products were found to be high in sodium and 40 percent of them high in fat.

The council's chief executive, Gilly Wong, urged people not to rely on seaweed as a major source of fibre.

"Please don't use seaweed to replace vegetables. Because some people have a very busy lifestyle, and occasionally they just think seaweed is also very high in fibre, and they can use seaweed to replace regular vegetables. That may not be the best way to absorb [fibre]," she said.