New research has shown that despite electronic cigarettes being marketed as a potentially safer alternative to normal cigarettes, they are still causing harm to the lungs.
Researchers from the University of Athens found the device causes an immediate increase in airway resistance among users, lasting for 10 minutes, meaning less oxygen is absorbed by the blood.
Could e-cigarettes damage lungs?
Electronic cigarettes are devices that deliver nicotine through a vapour, rather than smoke.
There is no combustion involved but the nicotine in the device is still derived from tobacco.
In a statement, professor Christina Gratziou, one of the study's authors, said: "We do not yet know whether unapproved nicotine delivery products, such as e-cigarettes, are safer than normal cigarettes, despite marketing claims that they are less harmful.
"We found an immediate rise in airway resistance in our group of participants, which suggests e-cigarettes can cause immediate harm after smoking the device.
"More research is needed to understand whether this harm also has lasting effects in the long-term."
The research was presented at the European Respiratory Society's Annual Congress in Vienna.