E-cigarette liquids may up asthma, allergy risk: Study.

ISLAMABAD -- Commonly sold e-cigarette liquids contain at least one substance classified as a health risk, such as those capable of causing asthma and allergy symptoms, researchers have found.

The researchers analysed each sample to find out exactly which chemicals were present and in what quantities.

Every liquid they tested contained at least one substance that has some level of risk to health according to the United Nations classification system, Medical Express reported.

These included methyl cyclopentanolone (found in 26.3 per cent of samples) and a-ionone (found in 8.7 per cent of samples), both of which "may cause allergy or asthma symptoms or breathing difficulties if inhaled", according to their classification.

Other substances, such as menthol (42.9 per cent of samples), ethyl vanillin (16.5 per cent of samples) and acetyl pyrazine (8.2 per cent of samples), are classified as "able to cause respiratory...