What Is Vape Juice Made Of? Every Ingredient in Vape Liquid

Four ingredients go into UK vape juice: propylene glycol (PG), vegetable glycerin (VG), flavourings and nicotine. Every e-liquid sold in the UK has been through MHRA testing and TPD compliance checks before it can legally reach a shelf, and those four ingredients are the only things allowed in the bottle.

Vape juice, vape liquid, e-liquid and e-juice all mean the same bottle, so everything below applies whichever name you use. Each vape juice ingredient is covered in turn, along with what the UK bans from e-liquid, what the device itself is made of, and how the manufacturing and testing process works.

The Four Vape Juice Ingredients

Propylene Glycol (PG)

The throat hit you feel when you vape comes mostly from PG. It is a thin, colourless liquid that also carries flavour molecules well. You will already know PG without realising it because the same ingredient goes into asthma inhalers, food products and stage fog machines. In e-liquid, PG usually makes up 30% to 50% of the total volume.

Most nic salt e-liquids use a 50/50 PG/VG split because pod kits and MTL tanks need thinner liquid to wick properly. Higher PG ratios give a stronger throat sensation with less visible vapour. UK regulations require all PG in e-liquid to be pharmaceutical grade.

Vegetable Glycerin (VG)

If you have ever seen big clouds from a vape, that is VG doing the work. It is a thick liquid made from vegetable oils with a slightly sweet taste, and the more of it in your e-liquid, the thicker the vapour gets.

Sub-ohm vapers go for 70/30 VG/PG shortfill e-liquids because the higher VG content gives bigger clouds and a softer throat hit. Outside of vaping, VG turns up in toothpaste, cough medicine and food production. A 90 day inhalation study found only limited biological effects with no signs of toxicity.

The VG vs PG guide on our blog covers ratios in more detail and how to match them to your kit.

Nicotine

UK law caps nicotine in e-liquid at 20mg/ml, and it must be pharmaceutical grade, the same quality that goes into NHS patches and gum. Not all vape juice contains nicotine though. 0mg options exist for vapers who have stepped down or just want the flavour.

Freebase nicotine and nicotine salts are the two types you will come across. Freebase hits harder at the back of the throat and is common in shortfills at 3mg to 6mg. Nic salts feel smoother at higher strengths like 10mg and 20mg, and most nic salt e-liquids use them. The nic salt strengths guide on our blog covers which strength works for different vaping habits.

Worth knowing: nicotine on its own is not a carcinogen. The harm from cigarettes comes from burning tobacco, which produces tar, carbon monoxide and thousands of other chemicals that do not exist in e-liquid.

Flavourings

Every flavouring used in UK e-liquid has to be food grade, and the manufacturer has to submit a full ingredient list plus emissions testing data to the MHRA before selling it. That approval process takes six months from start to finish.

Emissions testing is the important bit. It heats the e-liquid to vaping temperature and analyses what compounds come off in the vapour. Some flavourings that are perfectly safe to eat behave differently when inhaled, so the heated output gets checked separately. Diacetyl and acetyl propionyl, both linked to respiratory issues in industrial settings, have been banned from UK e-liquids since 2016 under TPD rules.

How Is Vape Juice Made in the UK?

Everything starts in an ISO 7 clean room. The PG and VG going into the mix must be pharmaceutical grade, and raw materials get tested for purity before anyone touches them. Mixing, bottling and quality checks all happen in controlled environments.

Once a batch is mixed, it goes through emissions testing. The liquid gets heated to vaping temperature and the resulting vapour is analysed for harmful compounds. All of that data, along with the full ingredient breakdown and toxicological reports, gets submitted to the MHRA at least six months before the product can go on sale.

After approval, the e-liquid goes onto the MHRA's public database and the manufacturer has to track any adverse events reported by users. UK e-liquid costs more than unregulated imports for exactly this reason, every bottle has six months of testing behind it.

Vape Ingredients Banned in the UK

UK regulations specifically ban several ingredients from e-liquids:

• Diacetyl banned since 2016 under TPD rules. This is the chemical linked to "popcorn lung" in industrial workers exposed to extremely high concentrations. It has not been permitted in UK e-liquid for nearly a decade.
• Acetyl propionyl banned alongside diacetyl due to similar respiratory concerns when inhaled at high levels.
• Caffeine and taurine stimulant additives are not allowed in UK e-liquid.
• Colouring agents artificial colours have no place in vape juice and are banned.
• Vitamin E acetate this was linked to lung injuries in the US in 2019. Those cases involved illegal THC cartridges, not regulated UK e-liquid. It has never been permitted in TPD compliant products.

Is Diacetyl in Vape Juice?

No. Diacetyl has been banned from UK e-liquid since 2016 when the TPD regulations came into force. The "popcorn lung" story originally came from workers in a US popcorn factory who breathed in huge amounts of heated diacetyl every day for years. The concentrations involved were nowhere near what was ever found in pre-regulation e-liquids, even back when diacetyl was still legal.

Any TPD compliant e-liquid from a UK retailer has been through emissions testing that specifically checks for diacetyl. It is not in the product.

Is Acetyl Propionyl Banned in UK E-Liquids?

Yes. Acetyl propionyl was banned at the same time as diacetyl under the TPD regulations in 2016. All UK e-liquids must pass emissions testing that checks for both compounds. Any product containing either one would fail MHRA approval and could not legally be sold.

What Is the Vape Itself Made Of?

The liquid is only half the question people ask. The device holding it is a short list of parts, and nothing in it burns:

• Battery: a rechargeable lithium-ion cell, the same chemistry as a phone
• Coil and wick: resistance wire wrapped in cotton, which heats the liquid
• Tank or pod: food-safe PCTG plastic or glass, holding the liquid
• Body: usually aluminium or zinc alloy

The battery heats the coil, the coil heats the liquid held in the cotton, and the result is vapour rather than smoke. Our guide to vape coils covers the heating side in full, and our beginner's guide to vaping explains how the parts work together.

UK E-Liquid Regulations: TPD and MHRA

The Tobacco and Related Products Regulations (TRPR) enforce the EU Tobacco Products Directive (TPD) across the UK. Every e-liquid sold legally has to meet these rules:

How to Check if Your E-Liquid Is TPD Compliant

The packaging tells you everything. A legally compliant UK e-liquid will have:

• MHRA registration number
• Full ingredient list printed on the label or leaflet
• Health warning covering 30% of the pack
• Childproof cap
• UK manufacturer or importer address
• Batch number

Anything missing from that list is a red flag. Stick to authorised UK retailers who only stock MHRA notified products.