What Is in Vape Juice? Every Ingredient Explained

Vape juice is four things: propylene glycol, vegetable glycerine, nicotine, and flavourings. In the EU and UK the full ingredient list has to be printed on the box, and most of the time that list is genuinely short.

The complication is that the bottle is not what you inhale. Heat changes the contents, and the coil adds things of its own. So the honest answer is four ingredients plus whatever the device makes out of them.

The four ingredients on the label

Propylene glycol (PG). A thin, colourless liquid used in food, medicines and stage fog. It carries flavour and produces the scratch at the back of the throat that ex-smokers tend to want. It is also hygroscopic, meaning it draws water from whatever it touches, which is why heavy vaping leaves you with a dry mouth and a dry throat.

Vegetable glycerine (VG). Thicker, faintly sweet, and responsible for the visible cloud. High-VG liquids feel smoother and clog coils faster. Most liquids are a blend, commonly somewhere between 50/50 and 30/70 PG/VG.

Nicotine. Extracted from tobacco or synthesised, then dissolved into the base. In the EU and UK, strength is capped at 20 mg/ml. In markets without that cap, 50 mg/ml salt liquids are standard in pods and disposables.

Flavourings. The interesting part. A single fruit flavour can be a blend of a dozen aroma chemicals, and this is where the ingredient list stops being informative, because “flavourings” is one word covering a very large space.

Why “food-grade” is not the reassurance it sounds like

Every flavour compound in e-liquid is approved for food. That approval means it has been assessed for being eaten, digested and metabolised by the liver.

Inhalation is a different route into the body. Aerosol goes to the alveoli, straight into the bloodstream, bypassing digestion entirely. A compound can be entirely safe to swallow and irritating or toxic to lung tissue, and almost none of the flavour chemicals used in e-liquid have been tested for chronic inhalation, because until recently there was no commercial reason to test them that way.

The known example is diacetyl, the compound that makes butter taste buttery. Swallowing it is fine. Inhaling it in industrial quantities caused irreversible airway scarring in microwave popcorn factory workers, which is where the phrase popcorn lung comes from. It is now banned in e-liquid in the EU and UK.

Diacetyl is the case that got resolved. Laboratory work on other common aroma chemicals, including cinnamaldehyde in cinnamon flavours and benzaldehyde in cherry and almond ones, has found effects on airway cells that plain PG and VG do not produce. That is cell-culture evidence rather than proof of disease in people, and it is a reasonable argument for treating “it’s just food flavouring” as marketing rather than science.

What is not in the bottle but ends up in your lungs

Two categories.

Thermal breakdown products. When PG and VG are heated hard, some of it decomposes into carbonyls, including formaldehyde, acetaldehyde and acrolein. At normal power with a wet wick the amounts are far below what cigarette smoke delivers. They rise sharply in dry-puff conditions, meaning a coil running with insufficient liquid, which is what that harsh burnt taste actually is. If a puff tastes scorched, that is chemistry telling you something, not a flavour flaw.

Metals. The coil is metal, and it sits in liquid at high temperature. Nickel, chromium and lead have been detected in aerosol in multiple studies, generally at low levels, generally higher in older or poorly made coils.

Freebase nicotine and nicotine salts

Worth understanding, because it explains most of modern vaping behaviour.

Freebase nicotine is alkaline, so at high concentrations it burns the throat. That harshness acted as a natural limit for years, which is why third-generation devices ran low strengths.

Nicotine salts add an acid, usually benzoic, which lowers the pH. High concentrations then go down smoothly. That is the whole innovation behind pods and disposables, and it removed the last brake on intake. Smooth means you can take three hundred puffs a day without discomfort, and most heavy users do.

What about zero-nicotine liquid?

It removes the drug and keeps everything else: the base liquid, the flavour chemicals, the heat, the hundreds of daily inhalations, and the hand-to-mouth loop that is doing at least half the work of the habit.

As a final step in a taper it can be useful. As a permanent destination it tends to be a holding pattern, and the return trip to a nicotine pod is short.

What to do with all of this

Not panic, and not shrug. The defensible position on ingredients is the same as the defensible position on vaping generally: substantially fewer harmful compounds than cigarette smoke, an unclear long-term picture, and a delivery system engineered so that you use it far more often than you would use tobacco.

The practical consequence is dose. Whatever is in the liquid, you are getting it in proportion to how many puffs you take, and almost nobody knows that number. People guess low, routinely by half.

Puff Counter is built around fixing that first: it counts the puffs you take on autopilot and then rebuilds each week’s limit from your own real average, so cutting down becomes arithmetic instead of willpower.

Here is the two-minute version you can do without an app. For the rest of today, mark a tally every time you take a puff. Do not try to cut down, do not judge the total. Just find out what your number actually is, because you cannot reduce a quantity you have never measured.