Nicotine electronic cigarettes (“e-cigs” or “vapes”) can damage people's health, especially children's,Oyella P, et al. Arch Dis Child 2026;0:1–7. doi:10.1136/archdischild-2025-330125 but are far less harmful than smoking. Electronic cigarettes increase the risk of asthma and chronic obstructive pulmonary disease (COPD) compared to not using nicotine at all. Pregnant women vaping may increase the risk of their children suffering from asthma and COPD. Vaping is associated with heart failure, and can cause seizures. Unregulated or modified e-cigs or liquids may be more dangerous than those whose production is well-regulated. Misuse, accidents, and product malfunction issues increase risks such as nicotine poisoning, contact with liquid nicotine, and severe burns.
Some of the most common but less serious adverse effects include abdominal pain, headache, blurry vision, throat and mouth irritation, vomiting, nausea, and coughing. People can become dependant on vapes. Nicotine is addictive and harmful to fetuses, children, and young people. However vaping while pregnant is less dangerous than smoking while pregnant. Passive e-cigarette vapor exposure may be harmful to children, but more studies are needed as of 2026.
Randomized controlled trials have provided "high-certainty" evidence that e-cigarettes containing nicotine are more effective than nicotine replacement therapy for discontinuing tobacco smoking, and moderate‐certainty evidence that they are more effective than e-cigarettes free of nicotine.
Harm reduction
When a person does not want to quit nicotine, harm reduction means striving to eliminate exposure to smoke by replacing it with vaping. E-cigarettes can reduce smokers' exposure to carcinogens and other toxic chemicals found in tobacco.
Tobacco harm reduction has been a controversial area of tobacco control. Health advocates have been slow to support a harm reduction method out of concern that tobacco companies cannot be trusted to sell products that will lower the risks associated with tobacco use. A large number of smokers want to reduce harm from smoking by instead using e-cigarettes. Quitting smoking is the most effective strategy for tobacco harm reduction.
Tobacco smoke contains 100 known carcinogens and 900 potentially cancer-causing chemicals, but e-cigarette vapor contains fewer potential carcinogens than tobacco smoke. A 2025 review of 39 studies found "no significant incident or prevalent risk" of cancer from vaping. Due to their similarity to traditional cigarettes, e-cigarettes could play a valuable role in tobacco harm reduction. The public health community remains divided concerning the appropriateness of endorsing a device whose safety and efficacy for smoking cessation remain unclear. Overall, the available evidence supports the cautionary implementation of harm reduction interventions aimed at promoting e-cigarettes as attractive and competitive alternatives to cigarette smoking, while taking measures to protect vulnerable groups and individuals. An evidence review commissioned by England's Office for Health Improvement and Disparities (OHID) concluded that, in the short and medium term, vaping poses a small fraction of the risks of smoking, while noting that vaping is not risk-free for people who have never smoked.
Evidence to substantiate the potential of vaping to lower tobacco-related death and disease is unknown. E-cigarettes could have an influential role in tobacco harm reduction. One study's authors warned against the potential harm of excessive regulation and advised health professionals to consider advising smokers who are reluctant to quit by other methods to switch to e-cigarettes as a safer alternative to smoking.
Smoking cessation E-cigarettes can help people quit smoking, but only about one in ten quit. Limited evidence suggests that e-cigarettes likely do help people to stop smoking when used in clinical settings. However, more smokers become dual users than succeed in complete abstinence. Outside clinical settings, vaping does not greatly change the odds of quitting smoking.
The public health community is divided over the use of these devices to reduce or prevent smoking. As of 2017, they were not approved by the US Centers for Disease Control and Prevention (CDC) as a smoking cessation product, and in 2020, they became regulated as a tobacco product, despite not containing tobacco. However, a 2019 study reported that 10% of participants given nicotine via gum, mouth spray, patches, etc., quit smoking, while 18% of those given vaping kits quit. Among study participants still smoking, e-cigarette users smoked less. A 2021 review by Public Health England (PHE) reported vaping to be around 95% less harmful than smoking. E-cigarettes are estimated to have preserved 677,000 life–years in the US alone from 2011 to 2019.
A small number of studies have looked at whether using e-cigarettes reduces the number of cigarettes smokers consume. It is unclear whether e-cigarettes are only helpful for particular types of smokers. Vaping with nicotine may reduce tobacco use among daily smokers. Whether vaping is effective for quitting smoking may depend on whether it was used as part of an effort to quit.
Evidence suggests smokers are more frequently able to completely quit smoking using tank devices compared to cigalikes, which may be due to their more efficient nicotine delivery. One study supports the claim that smokers are more likely to use e-cigarettes as a nicotine replacement product to aid in smoking cessation than other pharmaceutical products.
There is low-quality evidence that vaping assists smokers to quit smoking in the long-term compared with nicotine-free vaping. Tentative evidence indicates that health warnings on vaping products may influence users to give up vaping.
There is robust evidence that vaping is not effective for quitting smoking among adolescents. In view of the shortage of evidence, vaping is not recommend for cancer patients, although for all patients vaping is likely less dangerous than smoking cigarettes. The effectiveness of vaping for quitting smoking among vulnerable groups is uncertain.
Safety
Ecigs are harmful to children, but there is no consensus on the risks of e-cigarette use by adults. There is little data about their safety, and a considerable variety of liquids are used as carriers, and thus are present in the aerosol delivered to the user. One 2025 study found no serious respiratory effects, whereas another found that vaping is associated with chronic obstructive pulmonary disease but less so than smoking. Regulated US FDA products such as nicotine inhalers may be safer than e-cigarettes, but e-cigarettes are safer than combusted tobacco products such as cigarettes.
The risk of early death is anticipated to be similar to that of smokeless tobacco. Since vapor does not contain tobacco and does not involve combustion, users may avoid several harmful constituents usually found in tobacco smoke, such as ash, tar, and carbon monoxide. However, e-cigarette use with or without nicotine cannot be considered risk-free because the long-term effects of e-cigarette use are unknown. There is "only limited evidence showing adverse respiratory and cardiovascular effects in humans", with the authors of a 2020 review calling for more long-term studies on the subject.
The cytotoxicity of e-liquids varies, and contamination with various chemicals have been detected in the liquid. Metal parts of e-cigarettes in contact with the e-liquid can contaminate it with metal particles.
Nicotine is associated with cardiovascular disease and poisoning, and possibly with birth defects. , there is insufficient evidence of cancer caused directly by e-cigarettes.
In 2021, researchers at Johns Hopkins University reported over 2,000 unknown chemicals in the vape clouds that they tested from Vuse, Juul, Blu and Mi-Salt vape devices.
E-cigarettes create vapor that consists of fine and ultrafine particles of particulate matter, with the majority of particles in the ultrafine range. The vapor have been found to contain propylene glycol, glycerin, nicotine, flavors, small amounts of toxicants, and heavy metals, as well as metal nanoparticles, and other substances. Exactly what the vapor consists of varies in composition and concentration across and within manufacturers, and depends on the contents of the liquid, the physical and electrical design of the device, and user behavior, among other factors.
The majority of toxic chemicals found in cigarette smoke are absent in e-cigarette vapor. E-cigarette vapor contains lower concentrations of potentially toxic chemicals than with cigarette smoke. Those which are present, are mostly below 1% of the corresponding levels permissible by workplace safety standards. But workplace safety standards do not recognize exposure to certain vulnerable groups such as people with medical ailments, children, and infants who may be exposed to second-hand vapor.
Addiction
Nicotine, a key ingredient in most e-liquids, is well-recognized as one of the most addictive substances, as addictive as heroin and cocaine. Addiction is believed to be a disorder of experience-dependent brain plasticity. The reinforcing effects of nicotine play a significant role in the beginning and continuing use of the drug. First-time nicotine users develop a dependence about 32% of the time. Chronic nicotine use involves both psychological and physical dependence. Nicotine-containing e-cigarette vapor induces addiction-related neurochemical, physiological and behavioral changes. Nicotine affects neurological, neuromuscular, cardiovascular, respiratory, immunological and gastrointestinal systems.
Neuroplasticity within the brain's reward system occurs as a result of long-term nicotine use, leading to nicotine dependence. The neurophysiological activities that are the basis of nicotine dependence are intricate. It includes genetic components, age, gender, and the environment. Nicotine addiction is a disorder which alters different neural systems such as dopaminergic, glutamatergic, GABAergic, serotoninergic, that take part in reacting to nicotine. Long-term nicotine use affects a broad range of genes associated with neurotransmission, signal transduction, and synaptic architecture. The ability to quit smoking is affected by genetic factors, including genetically based differences in the way nicotine is metabolized.
Nicotine is a parasympathomimetic stimulant that binds to and activates nicotinic acetylcholine receptors in the brain, which subsequently causes the release of dopamine and other neurotransmitters, such as norepinephrine, acetylcholine, serotonin, gamma-aminobutyric acid, glutamate, endorphins, and several neuropeptides, including proopiomelanocortin-derived α-MSH and adrenocorticotropic hormone. Corticotropin-releasing factor, Neuropeptide Y, orexins, and norepinephrine are involved in nicotine addiction. Continuous exposure to nicotine can cause an increase in the number of nicotinic receptors, which is believed to be a result of receptor desensitization and subsequent receptor upregulation.
Long-term exposure to nicotine can also result in downregulation of glutamate transporter 1. Long-term nicotine exposure upregulates cortical nicotinic receptors, but it also lowers the activity of the nicotinic receptors in the cortical vasodilation region. These effects are not easily understood. With constant use of nicotine, tolerance occurs at least partially as a result of the development of new nicotinic acetylcholine receptors in the brain.
After several months of nicotine abstinence, the number of receptors go back to normal. The extent to which alterations in the brain caused by nicotine use are reversible is not fully understood. Nicotine also stimulates nicotinic acetylcholine receptors in the adrenal medulla, resulting in increased levels of epinephrine and beta-endorphin.