Driving accidents involving people under the influence of legal drugs such as hay fever remedies have soared by 600% in the last decade, figures have shown.

The British Allergy Foundation, which is launching a Drive Against Drowsiness campaign, said the problem could become as serious a threat to road safety as drink-driving.

Numbers of drink-driving accidents have fallen by two-thirds in the last 10 years, due to a government crackdown.

The campaign, which aims to raise awareness of the dangers of taking medication before driving, is supported by major motoring organisations.

The increase in road traffic accident fatalities linked to drug-driving is extremely worrying Muriel Simmons British Allergy Foundation

Unlike alcohol, there is no legislation restricting intake of legal drugs and driving. Studies reveal that one in five drivers are potentially driving "under the influence" of medication.

Legal drugs such as antihistamines, which are often the primary treatment for hay fever but can cause drowsiness, are being increasingly prescribed as more people develop the allergy.

'Other options'

Muriel Simmons, chief executive of the British Allergy Foundation, said: "The increase in road traffic accident fatalities linked to drug-driving is extremely worrying.

"Although people are becoming more aware of the dangers of drowsiness, many are still unaware that there are other options available to them such as truly non-sedating antihistamines which their GP can prescribe for them."

Most antihistamines in the marketplace are often misleadingly described as non-sedating Professor Ian Hindmarch University of Surrey

She said that medication affects different people in different ways.

But she added that those taking it were often unaware that their reaction times could be even slower than if they had been drinking.

Professor Ian Hindmarch, of the University of Surrey, said: "Most antihistamines in the marketplace are often misleadingly described as non-sedating - but they do cross into the brain and cannot really be non-sedating even if taken at the recommended dose.

"Unfortunately, when hay fever is at its peak, it is all too tempting for the sufferer to exceed that dose, and this can lead to tiredness and reduced ability to carry out daily tasks.

"The only true non-sedating antihistamine and, therefore the safest option, is one that does not cross into the brain and remains non-sedating at any dose."

Experts had one final warning for hay fever sufferers.

They say that sneezing while driving at 70mph could mean travelling 300ft with your eyes closed, which could potentially lead to a fatal accident.