what is nicotine

July 7, 2026

What Is Nicotine?

A clear guide to what nicotine actually is, where it comes from and how it works.

In brief: Nicotine is a naturally occurring chemical compound found primarily in tobacco plants. It is a stimulant that acts on receptors in the brain, producing alertness, dopamine release and, with regular use, dependency. It is the addictive substance in cigarettes and vaping products but is not the main cause of smoking-related diseases.

Nicotine is one of the most familiar substances in the world yet also one of the most misunderstood. Much of the confusion comes from its close association with tobacco, leading many people to conflate nicotine with the much broader harm profile of smoking.

The Basics: What Nicotine Is

Nicotine (chemical formula C10H14N2) is an alkaloid: a naturally occurring nitrogen-containing compound produced by plants primarily as a deterrent to insects. The tobacco plant (Nicotiana tabacum) is the most concentrated source, but nicotine is also present in smaller amounts in other nightshade family plants including tomatoes, potatoes, aubergines and peppers. The concentrations in food are far too low to have any physiological effect.

At room temperature, pure nicotine is a colourless to pale yellow oily liquid. It is water-soluble and absorbed rapidly through mucous membranes, the skin, the lungs and the gastrointestinal tract.

How Nicotine Works in the Body

Stage	What happens	Effect experienced
Absorption (seconds)	Nicotine passes through the lung lining or oral mucosa into the bloodstream	Rapid onset: within 10 to 20 seconds of inhalation
Brain receptors (seconds to minutes)	Nicotine binds to nicotinic acetylcholine receptors (nAChRs) in the brain	Release of dopamine, noradrenaline, serotonin: alertness, mood lift
Adrenal stimulation (minutes)	Nicotine triggers adrenaline release from the adrenal glands	Heart rate increase, blood pressure rise, mild energy boost
Metabolism (1 to 2 hours)	Liver converts nicotine primarily to cotinine; half-life approximately 1 to 2 hours	Effects wear off; nicotine levels fall; withdrawal symptoms begin in dependent users
Dependency (ongoing)	Brain adapts by increasing nAChR expression; requires nicotine to feel normal	Cravings, irritability and anxiety when nicotine is absent

Where Nicotine Comes From in Vaping Products

The nicotine in UK e-liquids is either extracted from tobacco plants or synthesised in a laboratory. Both forms are chemically identical and produce the same physiological effects. Laboratory-synthesised nicotine (sometimes called tobacco-free nicotine or TFN) produces no tobacco-derived impurities and is increasingly used by e-liquid manufacturers.

In the UK, e-liquid nicotine must come in two main forms: freebase nicotine (the traditional form) and nicotine salts (formed by combining freebase nicotine with an organic acid to create a smoother, faster-absorbing formulation used in most pod systems today).

Nicotine concentration in common sources (approximate, relative)

Shows how concentrated nicotine is across sources: food sources are negligibly small.

Tobacco leaf (dry)

Up to 3%

E-liquid (UK max)

2% / 20mg/ml

Tomato (fresh)

Trace only

Frequently Asked Questions

Nicotine is toxic at high doses. The estimated lethal dose for an adult is around 30 to 60mg absorbed (though some research suggests the true figure is higher). At the concentrations in e-liquid (up to 20mg/ml), swallowing a small quantity could cause significant illness. This is why e-liquids must be stored safely and child-proof caps are required. In normal vaping use, the amounts absorbed per session are far below toxic levels.

Nicotine itself is not classified as a carcinogen (cancer-causing substance) by major health bodies. The carcinogens in tobacco smoke come from combustion byproducts, not from nicotine. Nicotine does have some cell signalling effects that have been studied in relation to tumour growth, but it is not considered a primary cancer-causing agent. The main health concerns from nicotine relate to dependency and cardiovascular effects.

Freebase nicotine is the pure form of the compound: unmodified, with a higher pH. It can feel harsh at higher concentrations in e-liquid, limiting how much can be used comfortably. Nicotine salts are made by combining freebase nicotine with an organic acid (typically benzoic acid), creating a lower-pH compound that is smoother to inhale and absorbs more efficiently into the bloodstream. This is why nic salts are used at 10 to 20mg/ml in pod kits: you get effective nicotine delivery without harshness.

Yes: small amounts of nicotine are present in several common food plants including tomatoes, potatoes, aubergines, peppers and cauliflower. However, the concentrations are so low (typically 0.01 to 0.1 micrograms per gram of fresh weight) that you would need to eat an extraordinary quantity to experience any physiological effect. These dietary sources are not a meaningful source of nicotine.

Browse all nicotine strengths and formulations at Celtic Vapours

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