Cosmetics buyers are warned to be on the lookout after a high number of products containing "dangerous chemicals" have been found.
A total of 15 cosmetic businesses in London were heavily fined last year for dealing with unsafe products.
Some of them contained harmful enough chemicals to cause organ damage, Trading Standards (TS) officials said.
The majority of the prosecutions concerned the supply of skin lightening products containing a cocktail of dangerous chemicals.
Using these kind of illegal products for a prolonged period of time can result in a host of health problems, from skin thinning and discoloration to organ damage and even cancer.
Fines totalling £168,579 were handed out to 17 individual company directors in a co-ordinated campaign that saw TS officers seize "hundreds and thousands" of products.
Steve Playle, a spokesman for London Trading Standards said: "Last year saw some great outcomes as a result of our co-ordinated campaign against illegal cosmetics and some defendants even had suspended prison sentences imposed.
"These penalties should make shop owners tempted to ignore safety rules think twice before putting profit over the health and safety of their customers."
Illegal sales do not just occur on the high street.
Research conducted for London Trading Standards Regional Intelligence Service has identified at least 15 online sellers of prohibited skin lightening products using internet auction site, eBay.
Work is now being done to locate and tackle these sellers.
Councillor Tom Miller, Brent Council cabinet member for stronger communities, said: "I’m really pleased to see that Trading Standards teams across London are working hard to stamp out the sale of these illegal, and quite frankly life threatening cosmetic products.
"Consumers have a right to expect that retailers will only sell safe and reputable products and businesses have a responsibility to make sure that each product they sell meets all the legal and safety conditions required by UK law.
"Our Trading Standards Team will continue to come down hard on these rogue retailers and ask people to report any concerns, so that Trading Standards can take action to prevent anyone being harmed or scarred for life."
Anyone with information about consumer crime can report it anonymously via the London Trading Standards reporting tool.
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