Hygge has a dark side. The Danish art of being cosy, specifically its association with the warm glow of candlelight, comes at a price: exposure to possibly dangerous levels of fumes and an increase in house fires.

Research on mice by scientists at Copenhagen University showed that exposure to particles from burning candles caused greater damage than the same dose of diesel exhaust fumes. Effects included lung inflammation and toxicity, arteriosclerosis, and ageing effects on chromosomes in the lungs and spleen.

“We don’t really understand why this is, there must be something special to these candlelight combustion particles,” said Prof Peter Møller, the study’s lead author. The issue is under-researched, he said.

Last week the Danish health authority’s scientific advice committee called for the concentration of particles from candles used indoors to be reduced.

“Danes burn more candles than anywhere else in the world, and we have a shorter life expectancy compared to other European countries,” said Prof Lars Gunnarsen, who sits on the committee.

The number of house fires increases in Denmark during December and January partly due to candle use. Photograph: Ann Pickford/Ann Pickford/Rex

“Probably a lot of this may be explained by smoking and drinking, but it could also be because we pollute our homes more with candles. We haven’t had a comprehensive epidemiological study, but the [Copenhagen University] work is alarming.”

Gunnarsen said he was in favour of “complete avoidance” of candles. “I think it is important. Many people become sick and die prematurely from particulate air pollution.”

Previous research has shown that 60% of ultra-fine particles in Danish homes stem from burning candles. Every Dane burns on average 3.5kg of candles a year, according to the Danish Lung Association.

On the same day the health authority committee’s report was released last week, the Copenhagen fire brigade was called out to two fires caused by candles. The number of house fires jumps by about 35% in December and January, partly because of increased candle use, said Mads Dalgaard of the Danish emergency management agency BRS.

“We have lots of candles inside homes so we can hygge; it is something we have done forever. But people do stupid things,” said Dalgaard.

Fire awareness in Denmark is extremely high, with frequent public information campaigns.

“Yet still there is a problem with hygge and candles – especially children and teenagers, who like to have hygge in their bedrooms,” said Marcello Francati, a fire prevention manager at the Copenhagen fire brigade. He advises people to switch to LED or battery-powered lighting, which can still bring plenty of hygge.

Hygge has become a lifestyle trend across Europe in recent years. The Danish word has no single literal translation, but broadly conveys a sense of cosiness.

“Hygge is a wonderful thing,” Dalgaard said. “But beware of candles.”