Police issued the shocking warning following a raid that saw more than 500 bottles – worth £40,000 – seized.
The horde is part of a number of fake cosmetics that have been found by cops also containing killer substances, such as arsenic, mercury and lead.
Dodgy dealers looking to make a few quid produce the knock-offs in run-down factories that are covered in rat poo and human waste.
City of London Police say products made in these conditions can cause everything from skin rashes to swelling and burns on unsuspecting customers.
Det Chief Insp Teresa Russell said: “Valentine’s Day is a counterfeiter’s dream. It’s easy to fall into the trap of a cheap offer.
“Fake make-up and perfume can contain harmful chemicals. And buying counterfeit goods online can mean your personal details are used to set up new fraudulent websites.”
Stopping the trade of counterfeit goods is a big task for authorities, with consumers spending approximately £90 million a year on fakes.
The Trading Standards website offers shopper plenty of advice in avoiding getting ripped off.
It states: “If something seems too good to be true, e.g. a Rolex watch being sold for £10, it probably is. Don’t be fooled into thinking you’re getting a great deal.
“Always examine the quality of any goods you’re thinking of buying and check the labels to see if they are genuine. It’s often very easy to spot a fake as their labels may have spelling mistakes or other distinguishing marks.
“Always ask the trader you’re buying from whether they offer an after-sales service, or a guarantee. Most rogue traders won’t.”