The Scottish painter Peter Howson has told of how he has been receiving treatment for a rare condition that affects his painting hand.

Howson, who is preparing for a major new show in the US in May, said he has been diagnosed with dystonic tremor, which made his right hand suffer from tremors.

The painter, whose Prophecy exhibition opens at the Flowers Gallery in New York in May, is now being treated with botox injections.

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He said: "It's been a bit worrying but I'm trying to make the best of it.

"One of the things I've had to do is change the way I hold my paint brush and write.

"Ironically I have a complete aversion to all kinds of cosmetic treatments and surgery so it's quite funny that I've had to turn to Botox injections in my wrist to allow me to continue my work. At least my hand is looking good."

Botox, also known as botulinum toxin, is used as a cosmetic drug to freeze muscle activity and remove lines and wrinkles on the skin, but has long been used to treat muscle spasms and conditions that affect muscles including cerebral palsy.

The artist, based in Glasgow, added: "Lack of sleep and long hours when I'm working for an exhibition are nothing new.

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"It goes hand in hand. But this was suddenly something different and the tremors and cramping in my right hand were making it increasingly difficult to write and to hold a brush.

"I'd be working on an intricate part of a painting, like an eye, and the brush would slip and cause a streak.

"I thought at first it might be Parkinson's, and, of course, I'm relieved it isn't.

"But it was a worry for a while and I knew I needed to get to the bottom of it."

Howson had hospital tests, including an MRI, and doctors concluded the tremors were caused by dystonia.

The artist added: "The botox has really helped. It has been a relief to get a diagnosis and get back to some sort of normality but the injections every three months are very sore."

Howson is preparing fifty pieces for the show, his first in eight years in New York, including four large paintings measuring eight foot by six foot, and several works on panel.

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Howson, 58, was the official British war artist in the 1993 Bosnian civil war.

The painter grew up in Prestwick, Ayrshire, and attended the Glasgow School of Art, and his works have, over the years, focused on muscular or looming male figures, war and Christian themes.

Howson was awarded the OBE in the 2009 Birthday Honours List but in 2014 said he was giving up the title as he did not want to be part of the "British Empire" and the UK involvement in wars in Iraq and Afghanistan.

Of the new works on panel, unusual for Howson, he said: "They are difficult to work on. They are taking ages. They are quite dark."