A food dye similar to the one used in blue M&Ms and liquorice allsorts could offer hope to people with spinal cord injuries, its only drawback being that it would briefly turn them blue.

In a study of rats the dye, known as brilliant blue G (BBG), reduced inflamation in the spinal cord and signifiantly improved long-term outcomes after injury.

An unforeseen side-effect of the treatment on rats was that their skin turned bright blue, leaving the white animals with bizarre blue noses, ears, paws and tails. The eyes of the albino rats turned from pink to a deep navy.

In the study, details of which are published today in the journal PNAS (Proceedings of the National Academy of Sciences ), rats were injected with either a high or low dose of BBG within 15 minutes of receiving a spinal cord injury. A control group was injected with water.

Both the groups given the BBG treatment showed much better long-term recovery than the control rats. After 42 days, the best-performing BBG rats were able to co-ordinate the movement of their front and back legs well enough to support their weight and walk. None of the control rats was able to do so.

Apart from their unusual appearance, the rats seemed not to suffer any ill effects. Their body temperature, blood pressure and weight were unchanged.

There was no difference in effectiveness between the two doses but the rats on the higher dose turned a deeper shade of blue.

All of the rats resumed their natural colour within a week.

The skin colouring could last longer in humans, however, as our metabolism is about eight times slower.

According to the scientists, the dye works by blocking the action of the chemical known as adenosine triphosphate, or ATP, that is responsible for inflammation in the spinal cord after injury. For spinal neurons, the inflammation often causes more serious and irreversible damage than the initial trauma. Typically, ATP floods the injured area and sends neurons into a firing frenzy until they eventually die. But the BBG dye has a stronger affinity for spinal neurons than does ATP and so blocks its action.

Crucially, the blue dye is effective because it is capable of crossing the blood-brain barrier and penetrating the spinal cord.

Although other chemicals have been found that can block ATP they were unable to cross the blood-brain barrier.

Between 36,000 and 40,000 people in Britain have a spinal cord injury and about 1,000 new cases occur each year. Many of them receive no treatment other than pain relief and physiotherapy.

The most common treatment is a high dose of steroids. However, steroids are effective only for milder injuries and given in only about 15 per cent of cases. Maiken Nedergaard, a neuroscientist at the University of Rochester in New York and a co-author of the study, said BBG could offer a more direct and effective treatment.

The study’s authors are hoping to begin trials with the treatment in people as soon as possible.

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