Calls to US poison control centres about people sickened by e-cigarettes containing liquid nicotine have soared in the past four years, health officials have warned.
The number of calls climbed from just one a month in 2010 to at least 215 per month this year, according to a report by the US Centres for Disease Control and Prevention (CDC).
The number of calls per month involving conventional cigarettes did not show a similar increase during the same time period, the report said.
More than half (51.1 per cent) of the calls to poison centres due to e-cigarettes involved young children under age 5, and about 42 per cent of the poison calls involved people aged 20 and older, CDC said.
The analysis compared total monthly poison centre calls involving e-cigarettes and conventional cigarettes, and found the proportion of e-cigarette calls jumped from 0.3 per cent in September 2010 to 41.7 per cent in February 2014.
Poisoning from conventional cigarettes is generally due to young children eating them.
Poisoning related to e-cigarettes involves the liquid containing nicotine used in the devices and can occur in three ways: by ingestion, inhalation or absorption through the skin or eyes.
"This report raises another red flag about e-cigarettes Ė the liquid nicotine used in e-cigarettes can be hazardous," said CDC Director Tom Frieden.
"Use of these products is skyrocketing and these poisonings will continue. E-cigarette liquids as currently sold are a threat to small children because they are not required to be childproof, and they come in candy and fruit flavors that are appealing to children," said Frieden.
E-cigarette calls were more likely than cigarette calls to include a report of an adverse health effect following exposure. The most common adverse health effects mentioned in e-cigarette calls were vomiting, nausea and eye irritation.
Data for the study came from the poison centres that serve the 50 states, the District of Columbia, and US Territories.
The study examined all calls reporting exposure to conventional cigarettes, e-cigarettes, or nicotine liquid used in e-cigarettes.
Poison centres reported 2,405 e-cigarette and 16,248 cigarette exposure calls from September 2010 to February 2014.
The total number of poisoning cases is likely higher than reflected in the study, because not all exposures might have been reported to poison centres, CDC said.
The report shows that e-cigarette liquids containing nicotine have the potential to cause immediate adverse health effects and represent an