Rates 50 per cent higher in those exposed to chemical solvents, but as much as 30 times higher in people among those who smoke.

Cleaners, hair stylists, decorators and anyone coming into contact with potent solvents in paint thinners and cleaning supplies are 50 per cent more likely more likely to develop multiple sclerosis (MS), a study has found.

The risk of developing the neurodegenerative disease is seven times higher in people who work with solvents and have a family history of it, according to research published in the journal Neurology. 

It was thirty times higher when you added smoking to the mix.

This suggests that constant lung irritation might be activating the immune system in a way that makes it more likely to trigger MS, a disease where immune cells malfunction and attack the body’s nerves.

“It’s possible that exposure to solvents and smoking may both involve lung inflammation and irritation that leads to an immune reaction in the lungs,” said the study’ author Dr Anna Hedström, from the Karolinska Institute in Stockholm, Sweden.

“These are significant interactions where the factors have a much greater effect in combination than they do on their own,” she added.

Independent academics said the findings suggest those working with solvents who have a family history of the disease should aim to cut down their smoking and chemical exposure.

Dr Hedström’s team looked at the health records of 5,000 people, including 2,042 who had recently been diagnosed with MS.

They were asked about their exposure to organic solvents, which are chemicals common in paints and thinners, varnish, nail polish, glues and cleaning products, as well as their smoking history.

To identify MS risk, the researchers used blood tests to look for two variations in genes associated with white blood cells which play a key role when the immune system malfunctions in MS. One variation makes the disease more likely, and one appears to be protective.

These are the best studied genetic traits for the disease, but it is still poorly understood what causes the immune cells to start destroying the outer coat of nerve cells – called the myelin sheath – which allows rapid electrical impulses to be sent.

Vitamin D levels, infection with the Epstein-Barr Virus (mono) and even obesity are all factors that have been considered.

Solvent exposure which can be through the skin, ingestion or inhalation has well-known neurological effects – it can cause temporary euphoria as well as permanent brain damage.

But it appears it is most significant to MS when in combination with other risks.

From the latest data, the Swedish team identified that a combination of genetic risk factors and exposure to solvents account for up to 60 per cent of a person’s chance of developing the disease. However the researchers say their subjects ability to identify regular solvent exposure may be a limiting factor in the results.

However independent researchers said it was “staggering” that adding smoking into this mix increased the risk of MS 30.3 times.

“How this cocktail of MS genes, organic solvents and smoking contributes so significantly to MS risk warrants investigation,” said Gabriele C. DeLuca, MD, DPhil, of the University of Oxford in the United Kingdom and a member of the American Academy of Neurology, in an accompanying editorial.

“In the meantime, avoidance of cigarette smoke and unnecessary exposure to organic solvents, particularly in combination, would appear reasonable lifestyle modifications to reduce the risk of MS, especially in those with a family history of the disease,” she added.