What are electronic cigarettes (e-cigarettes)? - Simple and Practical Mental Health

Electronic cigarettes have come into widespread use in recent years. They are also called e-cigarettes or “vapes,” and using them is commonly referred to as “vaping,” although, technically, these devices produce an aerosol and not vapor.

How do they work?

The basic principle of how they work is simple. E-cigarettes contain a liquid, sometimes called an “e-liquid” or “juice.” It typically contains:

– A mixture of glycerol/glycerine and propylene glycol

– Nicotine extracted from tobacco

– Sometimes, other products for making the e-cigarette “more satisfying” or to feel more like smoking a cigarette

– Often, some kind of flavor.

The liquid is heated to create an aerosol that the person inhales, similar to smoking a cigarette.

So, even though they are called “cigarettes”, they don’t contain tobacco, and matches or a lighter are not needed for using them.

But the person exhales vapor that looks similar to cigarette smoke (see photo below) and leads to the term “vaping.”

Multiple generations of e-cigarettes

E-cigarettes have evolved considerably since they were first introduced. So, the available products are called first-generation, second-generation, third-generation, and so on.

The first-generation e-cigarettes are quite simple in design and look like cigarettes. See photo below. These deliver less nicotine, are less satisfying to patients, and are not recommended (Hartmann-Boyce et al., 2018).

Second-generation e-cigarettes (or “vape pens”) are more elaborate in design. See photo below. If a person wants to use e-cigarettes to quit smoking, these are the types recommended.

A second-generation product that looks a bit different is probably the most popular e-cigarette in the US as of September 2018. The brand name is JUUL (www.juul.com). See photo below. JUUL uses replaceable “pods” containing the liquid, which is available in many flavors. The pods provide a relatively high dose of nicotine (5%), but the dose of nicotine delivered by any e-cigarette depends significantly on how the system is used. JUUL pods are also available in 3% nicotine strength. (This paragraph about JUUL and the photo below are provided for general information only and are definitely not an endorsement of the product.)

Third-generation and fourth-generation e-cigarettes are complex in design and offer variable power settings. See photo below. These may be too complicated for a person new to e-cigarettes to use (Hartmann-Boyce et al., 2018).

Electronic nicotine delivery systems (ENDS)

First, a quick note on terminology. The umbrella term electronic nicotine delivery systems (ENDS) includes all devices that are commonly called e-cigarettes or “vapes.” Other terms for devices included under the term ENDS are vape pens, e-hookahs, hookah sticks, mods, personal vaporizers, and so on (Malani and Walter, 2024).

In a nutshell, ENDS are battery-powered devices that produce an aerosol by vaporizing an e-liquid containing nicotine and other substances, typically including propylene glycol and/or glycerin (Sharma et al., 2025).

Guides for patients

The CDC provides information about electronic cigarettes at THIS LINK.

Do electronic cigarettes (e-cigarettes) work for smoking cessation?

What “authorities” say about e-cigarettes for tobacco use disorder

References

Hartmann-Boyce J, Begh R, Aveyard P. Electronic cigarettes for smoking cessation. BMJ. 2018 Jan 17;360:j5543. Review. PubMed PMID: 29343486.

Malani PN, Walter KL. What Are E-Cigarettes? JAMA. 2024 Sep 3;332(9):768. doi: 10.1001/jama.2024.14334. PMID: 39110431.

Sharma S, Meister M, Weaver S, Zelikoff J, Bell-Huff C, Black M, Shannahan J, Wright C. The beginning of ENDS (electronic nicotine delivery systems): origins, trends, and regulatory considerations. Inhal Toxicol. 2025 Oct-Nov;37(9-10):417-425. doi: 10.1080/08958378.2025.2479518. Epub 2025 Mar 27. PMID: 40146120.

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