Soaps made from human breast milk have been hot-selling products on online marketplaces in China recently. But experts question such products' safety and effectiveness, according to a report in Beijing Youth Daily.

A soap retailer from Taizhou, Zhejiang province, said her products were manufactured from her own and her sister's leftover breast milk after they fed their babies, so the products are safe and healthy.

But because the soaps are produced at home and sold online, the report said, it's difficult to know whether the ingredients or the manufacturing processes are safe.

A manufacturer and seller surnamed Wang said handcrafted breast-milk soaps are popular with her relatives and friends because they effectively soften skin. She mainly makes breast-milk soaps with natural oils and lye, which she believes helps to kill bacteria, the news report said.

Doctors have raised medical concerns about breast-milk soaps, saying they could pose a health threat to users since viruses that cause diseases like AIDS or syphilis can be transmitted if the milk comes from a mother who is in poor health, an unnamed dermatologist was quoted as saying.

A search on Taobao.com, a major Chinese online trading platform, shows that more than 3,800 retailers on Taobao are selling breast-milk soaps at prices ranging from 20 yuan ($3) to 100 yuan, the report said.

They also sell DIY kits to give consumers directions on how to make breast-milk soaps at home.

Most sellers on Taobao claim that their soaps are made from 100 percent pure human breast milk, and that it can "whiten and protect" the skin.