PROPYLENE GLYCOL (PG)
What exactly is it?
Propylene Glycol Structure
PG stands for Propylene Glycol, a petroleum by-product. The fluid has no odour or colour, and is less viscous than VG. In vaping it is used to provide a 'throat hit', which some users claim is similar to the sensation experienced when smoking tobacco. It also carries flavour more effectively than VG, meaning it's the most commonly used suspension fluid for flavour concentrates and nicotine.
How is it used?
Propylene Glycol can be found in various common household items. Amongst others, these include:
- Asthma inhalers
- Pet food
- Medical products used orally, injected or as topical formulations
- Beauty products, including make-up, shampoo and baby wipes
Is it safe?
Studies have shown that PG is safe to ingest orally, and the FDA has deemed it "generally recognized as safe" to be used as a food additive. However, most studies into the safety of propylene glycol look at ingestion, rather than consuming it in aerosol form. Of the limited studies that exist, a long-term experiment held in 1947 judged that inhaling PG was 'completely harmless'. A 2010 study looking at PGEs (a mixture of propylene glycol and glycol ethers) suggested an increased risk of developing respiratory and immune disorders in children, such as asthma, hay fever and eczema. However, it was judged that glycol ethers, and not PG, are the more likely cause. Looking at the evidence, it is sensible to assume that PG is safe to be inhaled, but there is a need for more comprehensive studies to confirm this.
Many misinformed scaremongering stories in the media claim that PG is a toxic substance used in anti-freeze. However, the dangerous substance referred to is actually ethyl glycol, a chemical which is closely related, but not used in vaping.
While PG is regarded as safe for humans, it can cause serious harm to pets. It is generally regarded as safe as a food additive for dogs, but has been linked to Heinz body anaemia in cats. Be careful when vaping around pets, particularly if you have cats and use PG in your e-liquid.
What should I be aware of when vaping PG?
Some people find a high level of PG irritating to the throat. Allergies to PG are rare, but have been reported. If you find yourself coming out in a rash, or suffering other unpleasant reactions after using PG-based e-fluid, you should look at using 100% VG juice instead. Many vendors are starting to offer this as an option.
- The most common side effects of using e-liquid containing propylene glycol are: dry mouth, sore throat and increased thirst. These symptoms usually last anywhere from a few days to a week as the body gets used to the propylene glycol. It is advised to drink more water and liquids then usual for the first few weeks of using your e-cigarette. Be aware that any unusual reactions could be side effects from quitting smoking, and not necessarily because of the PG.
VEGETABLE GLYCERIN (VG)
What exactly is it?
VG stands for Vegetable Glycerin. It is a natural chemical, derived from vegetable oil, so is safe for vegetarians. It is commonly used in e-liquid to give a 'thick' sensation to vapour. VG has a slightly sweet taste and is considerably thicker than PG. The hit from a high VG fluid is a lot smoother than with PG, making it more suitable for sub-ohm vaping. While nicotine and flavourings are commonly suspended in PG, some vendors are offering a VG alternative, to enable 100% VG mixes.
What is it used for?
Sweetner and Sugar
Again, it can be found in numerous medical, food and personal care products:
- Sweetener as sugar replacement
- Beauty products, such as make-up, mousse, bubble bath, aftershave, and deodorant
- Pet food
- Soap and hand cream
- Food such as baked goods, to increase moisture
- To provide thick gel for certain medicinal creams, capsule pills and jellies
- Toothpaste and other dental care products
Is it safe?
The FDA has classified VG as "generally recognized as safe" and it is widely regarded as one of the most benign substances known to man. The SIDS assessment profile show it to have low toxicity when consumed, and of low potential to irritate the skin or eye. This, along with the widespread use of VG in food and medicine suggest it is safe for humans. However, as with PG, there are limited studies on VG being inhaled as opposed to ingestion. A 2008 study of the toxicity of inhaling aerosolised glycerol found minimal risks. We can assume the use of VG in vaping has no serious impact on health but, as with PG, we would welcome more detailed studies.
It is important to note that the risk of being allergic to vegetable glycerin is very low, making it a useful alternative for people who have issues when vaping e-juice containing PG. If you are allergic to palm oil or coconut oil then VG could prove a problem, but this is relatively uncommon. Diabetics could possibly experience problems with metabolising VG, but this would not be an issue at the levels used in vaping.
What should I be aware of when using VG?
The increased thickness of VG means it can reduce the life of atomisers quicker than PG-based juice. High VG liquids clog up coils more rapidly, and will not work well, if at all, in certain tanks. Older products are especially susceptible, particularly models that use smaller coils such as clearomizers. The Nautilus range, Innokin iclears and eGo tanks are some of the more well-known tanks that are known to have difficulties dealing with high VG fluid.
The most common side effect of vaping high VG e-liquid is a dry mouth, sore throat, and increased thirst. Again, be sure to drink plenty of water and take a break from vaping if necessary.
What PG/VG ratio should I use?
There isn't a one-size-fits-all answer to this. It depends on the kind of vaping experience you prefer. Many people use various levels of PG and VG for different purposes:
Throat Hit – If you enjoy a sharp throat hit when vaping then you’ll prefer a high PG vape. The ‘kick’ at the back of the throat, is something many ex-smokers crave, and PG (along with the nicotine) provides more of this than VG. PG carries flavour marginally better than VG, so the flavour will be slightly improved.
Smoothness – High VG fluid tends to give a much smoother feeling on the throat, with a more substantial ‘thicker’ mouthfeel. The flavour is slightly muted in VG fluids, but this can be countered by using more power to produce more vapour. Be careful to stay within the voltage/wattage limits of your atomiser, or you risk dry hits, or even damaging your equipment.
Stealth Vaping – If you want to keep your vaping lowkey in public then high PG is the way to go. Less vapour is produced when exhaled, making this ideal for the less ostentatious vaping enthusiast. However, you should always apply common sense. Vaping in certain places, such as waiting rooms and on public transport, is often outlawed and is simply bad manners. As vaping is relatively new, we have a duty to be aware of public opinion and behave responsibly.
Cloudchasing – A growing trend in vaping circles is ‘cloudchasing‘. This simply involves exhaling dense clouds of vapour, the thicker the better. There are even competitive events based around this activity, where the person producing the biggest clouds wins. If this appeals then high VG is the only option – the higher the better.