Mountain Dew drinks, Jolly Ranchers, Swedish Fish and Lemon Heads are being advertised on TikTok and Instagram.
But they are said to contain carcinogenic and genotoxic ingredients banned here.
Officers from the Chartered Trading Standards Institute recently swooped on £8,000 of illegal confectionary from 22 shops in Staffordshire. And more than £300 of banned sweets were found in a store in Burton-upon-Trent, including Jolly Ranchers hard candies containing mineral oil.
If this is contaminated with other compounds, it can initiate cancer formations, a BBC Morning Live investigation claimed.
US manufacturers have reportedly defended themselves, saying they are not involved with the sale of their products here.
Stephanie Young, team leader at CTSI in Staffordshire, said: “People are selling these products not realising they have banned ingredients in them.”
Calcium disodium EDTA, which is not allowed in drinks in the UK, was found in Mountain Dew. In studies, the crystalline powder caused adverse reproductive and developmental effects and has been shown to contribute to cancer of the colon.
Emeritus Professor Erik Millstone, from the University of Sussex, said the amount of banned products is concerning but added: “Don’t panic about anything you’ve done, but if you can avoid them, that’s prudent.