US health authorities have issued an alert over e-cigarette products after dozens of teenagers and adults have been struck with severe respiratory illnesses.
Doctors have warned about the risks of using products containing THC, the active ingredient in marijuana, or products bought off the street.
The Centers for Disease Control and Prevention (CDC) said that 215 teens and adults in 25 states, including Illinois, have contracted severe respiratory illnesses after vaping.
The CDC said in many of the cases patients had acknowledged they'd recently vaped a substance containing THC, the high-inducing ingredient in marijuana.
But the health authority also warned against modified products, and products purchased on the street.
This week, a teenager who was placed in a medically-induced coma with a rare lung disorder has claimed that her illness was down to years of vaping.
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Maddie Nelson, 18, has urged the public not to use the pens, popular among teenagers, which she smoked every day for three years.
In a heartfelt post on social media, Ms Nelson said: "I am sharing my story so you all are aware that there is something crazy in these pens that is not safe and almost cost me my life.”
CDC director Robert Redfield and US Food and Drug Administration (FDA) acting commissioner Ned Sharpless said in a statement: ‘Anyone who uses e-cigarette products should not buy these products off the street and should not modify e-cigarette products or add any substances to these products that are not intended by the manufacturer.
‘Regardless of the ongoing investigation, e-cigarette products should not be used by youth, young adults, pregnant women, as well as adults who do not currently use tobacco products.
Kevin Burns, the chief executive officer of electronic cigarette firm Juul Labs, said that his advice to current non-smokers was: ‘Don't vape. Don't use Juul. Don't start using nicotine if you don't have a pre-existing relationship with nicotine. Don't use the product. You are not our target consumer.’
A report by Public Health England said the devices are '95% safe' - but 'must be clearly positioned as products that help adult smokers to quit’.
Cancer Research UK said: ‘Studies show that levels of key harmful chemicals are lower in people who switch from tobacco to e-cigarettes. There are still some questions about long-term safety, as e-cigarettes haven’t been around that long.
‘But the evidence is pointing towards them being far less harmful than tobacco.
‘In terms of safety, e-cigarettes are likely far closer to nicotine replacement therapy (NRT). NRT has long been known as a much safer alternative to smoking.’