Inhaling paint and varnish fumes may increase the risk of multiple sclerosis, Swedish research shows.
On their own, the solvents raised the likelihood of developing MS by 50 pere cent when compared with no exposure.
Adding MS susceptibility genes to the equation led to an almost seven-fold increase in risk, a study found.
And a triple whammy of smoking, genetic risk factors and solvent exposure caused the relative risk to soar 30 times over.
Lead researcher Dr Anna Hedstrom, from the Karolinska Institute in Stockholm, said: "These are significant interactions where the factors have a much greater effect in combination than they do on their own.
"More research is needed to understand how these factors interact to create this risk. 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."
For the study, the researchers identified 2042 Swedes who had recently been diagnosed with MS and matched them with almost 3000 members of the general population.
Participants underwent blood tests and were asked whether they had ever smoked or been exposed to organic solvents, painting products or varnish.
MS genes and solvent exposure combined were responsible for an estimated 60 per cent of the overall risk of developing multiple sclerosis.
The findings are reported in the journal Neurology.
