A US Senate hopeful in the state of Montana has a bad case of the blues after years of drinking a home-made silver solution for medical reasons.

Libertarian candidate Stan Jones, 63, first discovered his skin was turning blue last year.

People ask me if it's permanent and if I'm dead - I tell them I'm practising for Halloween

Stan Jones

He began taking colloidal silver in 1999 amid fears that disruptions caused by the millennium bug might lead to a shortage of antibiotics.

His condition, known as argyria, is not serious.

Mr Jones is one of three candidates challenging Democrat Max Baucus for a Senate seat in November's mid-term elections.

Anthrax 'treatment'

He made the solution by electrically charging two silver wires in a glass of water.

"People ask me if it's permanent and if I'm dead," he told the Associated Press news agency. "I tell them I'm practising for Halloween."

Colloidal silver is marketed as an anti-bacterial agent or immune-system booster.

Along with other dietary supplements, it was offered as a treatment for illnesses such as anthrax following bio-terror alerts in the US last year. But there is no scientific proof of its efficacy.