Certain flavoured e-cigarettes, even without nicotine, may change how airways, affected by an allergic disease, function, thus worsening the severity of diseases such as asthma, say researchers.

For the first time, a model of asthma was used to investigate the effect of a range of popular e-cigarette flavours, with and without nicotine.

"This is especially important for those with respiratory disease, whom are vulnerable to the effects of smoking," Dr Chapman said.

"The majority of e-cigarette smokers use flavoured liquids but there is some evidence that flavour additives can be toxic when inhaled," said Dr David Chapman from from the University of Technology Sydney (UTS).

The use of e-cigarettes has dramatically increased in the past few years, especially among younger smokers globally.

Despite the suggestion they are a healthier alternative to tobacco cigarettes, there is a lack of evidence in both animal studies and human data on the effect of e-cigarettes on lung function.

The researchers found that some flavoured e-cigarettes, even in the absence of nicotine, can worsen disease severity.

"The exact effects on features of asthma were dependent upon the specific flavour, suggesting not all flavoured e-cigarettes will have the same consequences on lung health," Dr Chapman said in the study published in Scientific Reports.

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In this study, the flavour Black Licorice exaggerated airway inflammation whereas Cinnacide had the opposite effect, suppressing airway inflammation.

The researchers didn't analyse the liquids directly, to confirm what they contained, however there is evidence from previous research that flavours categorised as "buttery/creamy" and "cinnamon", which likely include "Banana Pudding" and "Cinnacide", respectively, are toxic.

Caution should be taken in promoting the use of flavoured e-cigarettes to patients with respiratory disease such as asthma and that policy makers should consider restricting the use of flavoured e-cigarettes, the team added. (IANS)