A Carmarthenshire company's magazine advert for a water purifier has been found to be misleading.
A2Z Ozone UK, which imports the device from the USA, said it aided respiration and produced youthful looking skin.
The Advertising Standards Agency (ASA) ruled that the firm, based in Cwmduad near Carmarthen, was unable to provide enough evidence to back up the claim.
The company said while it stood by the claims made in the advert it would not run it again.
The ASA investigated the advert following a complaint.
A2Z Ozone UK said ozone was used in the UK in the sanitisation of public and hospital swimming pools and they believed that this was proof of ozone's effectiveness as a sanitizer.
They said the supplier of the water purifier was based in Kentucky and the US Food and Drug Administration had changed its regulations to permit ozone generation as an anti-microbial agent.
They submitted a list of scientific and medical references regarding ozone from their supplier.
But the ASA ruled: "We did not consider that the document provided enough evidence to support the efficacy claims made in the ad.
"Moreover, we noted that we had not seen any evidence that the water purifier contained ozone generating technology.
"We therefore concluded that the claims had not been substantiated and that the ad was misleading."