A handful of diet or "detox" teas have been pulled from supermarket shelves following a Consumer NZ investigation.
Consumer NZ found that a selection of teas sold by the company Healtheries, owned by Vitaco Health, contained senna, a source of sennosides, a medicine used to treat constipation, which can only be sold in pharmacies.
Companies selling products that contain senna need consent from Medsafe. However, Healtheries' "Naturally Slim Lemon Tea", "Naturally Slim Superfruit Acai and Blueberry Tea", and "Herbalax Senna Peppermint Tea" teas were found to have no approval.
Senna Klenz, another brand of tea promoted as a detox tea and sold at health food stores, and a senna "teatox" advertised by influencer and personal trainer Sera Lilly on her website fat2fitnz.co.nz, were also found to contain the ingredient and not have approval from Medsafe.
Countdown and Foodstuffs, the owner of the New World and Pak'nSave brands, have now removed the teas from their shelves.
Health 2000 has also pulled the products from its shelves.
Healtheries Naturally Slim teas advertised "fresh-tasting blend of herbs formulated to complement your weight management program" and made claims about being a "detoxifier" that "assists with liver and kidney cleansing".
Consumer NZ chief executive Sue Chetwin said it was it was concerning that these companies did not appear to be aware of the rules around senna.
A natural laxative, senna can lead to liver damage if taken for too long, Chetwin said.
Advertising or selling pharmacy-only medicines, such as senna, without consent can result in a fine of up to $100,000.
"These types of products make various claims about weight loss or 'detoxing' but they can be little more than laxatives in disguise," Chetwin said.
"There's no good evidence these products provide any benefits and they could even do you harm."
She advised consumers not to waste money on diet and detox teas.
"You don't need to buy a pricey tea to 'detox'. Your body is already primed to get rid of toxins by itself."
Consumer said anyone who had bought the teams was entitled to a refund.