A woman’s teeth looked as though they had been dipped in acid after she had whitening treatment aboard a cruise ship, a dentist said yesterday.

Carla Regan, 47, was on a two-week cruise in the Eastern Mediterranean with her husband and two children when she decided to treat herself to the £130 treatment. But she was left with yellowing, easily stained and dry teeth after a chemical typically used for disinfecting swimming pools stripped away the top layer of tooth enamel on her front eight teeth. The treatment, using chlorine dioxide, was of a kind increasingly being offered to consumers wishing to brighten up their smile, despite evidence that it causes harm. Mrs Regan is now facing a £5,000 bill to restore her mouth’s appearance.

The General Dental Council has determined that only a registered dentist can carry out teeth whitening, yet the cruise ship treatment was provided by beauticians in an onboard spa, with no dentist even to supervise, she said.

Mrs Regan said yesterday: “The beauty salon on the ship was offering teeth whitening and I thought to myself, why not? It seemed like an appropriately indulgent thing to do on holiday – they promoted it as nontoxic and safe. However, a week later I noticed my teeth were starting to look stained, and with time they only got darker. I also constantly had a ‘dry mouth’ feeling, so I decided to see a dentist to tell me what could be wrong.”

Mrs Regan declined to name the cruise operator involved as she has lodged a formal complaint against the company.

“I had never considered whitening procedures before, and on the ship I had no chance to do any research into the treatment,” she said. “I thought it would be perfectly safe, but in the end it permanently damaged my teeth.”

James Goolnik, a dentist and vice-president of the British Academy of Cosmetic Dentistry, said he was shocked at the surface harm on Mrs Regan’s teeth. “Her teeth look like they had been dipped in acid,” he said. “It may not be immediately visible to the untrained eye, but her front teeth clearly have no surface shine when compared with the rest of her teeth. The damage is permanent and we are currently assessing whether repair will involve more complex cosmetic procedures, such as bonding or porcelain veneers.” Despite a lack of clinical evidence or official trials that justify the use of chlorine dioxide on teeth, the chemical is being offered as an alternative to hydrogen peroxide treatments by a growing network of franchises around the country.

Its use has caused problems in other patients, including 23-year-old Stephanie Ramezan, whose teeth were left darkened after a session at a City spa, as The Times reported in February.

Dr Goolnik said: “The rise in these problem cases illustrates why dental care, even purely cosmetic procedures, should only be provided by dentists with the proper training.”

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