Six syringes, a pot of cod liver oil, and seven glass vials have been neatly arranged on a blanket and photographed for a listing on the secondhand marketplace app Depop. Two blister packs of fertility supplements lie next to them, covering a third packet which has torn foil and capsules missing.

“Womens Fertility Trying To Concieve Vitamins & Supplements IVF,” reads a typo-laden caption for the items. “I am not a doctor, take at your own advise,” urges the seller, based in Milton Keynes, England.

Across the teen-focused reselling app, buyers can browse hundreds of health products and supplements, ready to purchase alongside secondhand clothes. Their suggested benefits, according to sellers, include acne “cleansing,” tanning, weight loss, erectile dysfunction help, and “skin-whitening.”

What isn’t immediately obvious is that these listings are illegal and could harm users, experts say. “You’re not meant to sell something that is prepacked when it’s been unsealed,” says Katrina Anderson, a UK ecommerce lawyer at law firm Osborne Clarke, who specializes in food industry and regulation issues. “If you’ve got an opened product, it could be contaminated with something.”

Founded in 2011, Depop is one of the world’s most popular reselling apps. The company says it has more than 30 million users in more than 150 countries, with 90 percent of active users under the age of 26. From vintage flares to handmade dresses, it has become synonymous with thrifting and more sustainable shopping globally. During the Covid-19 pandemic, its user base more than doubled, according to data from Statista, while over half of US and UK consumers spent more on health products, including supplements, according to Trustpilot. The interest extends to Depop, where users are “liking” and buying health-related items in droves. However, the platform is also home to a growing unregulated market of food products, with users flogging secondhand supplements.

WIRED found at least 208 listings for supplements and nearly 100 protein products for sale in the UK, with more than a dozen making unfounded health claims, and there was no evidence that sellers were authorized to sell supplements. Supplements are legally treated as food in the UK, requiring sellers to register as a food business operator with their council, a law that applies to anyone selling supplements online, including on marketplace apps. Yet all the “shops” were absent from the Food Standard Agency’s (FSA) database of food businesses, and no registrations were found by local authorities. Depop did not respond to WIRED’s request for comment.

A London-based seller advertised skin “whitening” products and supplements, which contain the antioxidant glutathione, an unproven chemical that the Food and Drugs Administration says may be dangerous. In the ad for whitening products, posted on the site a year ago, the seller boasted that the product could “Prevent Dull Skin Problems Dark Spots, and Increase Skin Clarity” and “Helping to Reveal Radiant Skin.” The seller, who had a five-star rating and reviews that raved about the products, did not appear to have a food business registration. They also advertised “collagen caps,” featuring a picture of a teenage girl holding the supplements and asserting without evidence that “usually collagen alone can make skin whiter clean,” “eradicate acne,” and “make the nipple color more pink.”