Thousands of home teeth-whitening kits with the potential to cause gum and mouth blisters have been seized in Hillingdon.
The products – together worth more than £500,000 – were seized from a residential property in Sipson.
Trading standards officers were called to the address in May 2014, by a resident who had allowed an acquaintance, Piotr Kaszubski, to store the products at his home, with a view to going into business with him.
The products contained 5.9% hydrogen peroxide, meaning they could only be legally supplied to dental practitioners - the limit for consumer products being 0.1%.
Trading Standards officers uncovered evidence that the goods were being supplied online to consumers without adequate checks.
Mr Kaszubski has now returned to his native Poland. According to the council, he said he was merely an agent for an American company, so the authority decided to seek forfeiture of the products.
Councillor Jonathan Bianco, cabinet member for finance, property and business services, said: "I am very pleased that officers have managed to take these items out of circulation.
"Products like this should only be used under the supervision of a qualified dental practitioner.
"We always put our residents first and our Trading Standards team work hard to identify and seize dangerous products, and prosecute when possible."
Teeth whitening products containing high levels of hydrogen peroxide should only be carried out under the supervision of a dental practitioner.
Stronger bleaching gel, if used incorrectly, can cause blistering and sensitivity on gums and in the mouth. Additionally, such treatment may not be suitable for all patients, the council warned.