When you shop online for e-liquid, you'll often see references to the PG and VG content of various products. The terms "PG" and "VG" refer to propylene glycol and vegetable glycerin, the two base liquids that an e-liquid may contain. Adjusting the ratio of the base liquids changes the experience that you'll have when vaping an e-liquid. Knowing the PG/VG ratio that works best for your needs helps to ensure that you'll always be happy with your e-liquid purchases.

Why Does E-liquid Need PG and VG?

PG and VG create the clouds that you inhale and exhale when you vape. They also dilute the nicotine and flavours in an e-liquid to create a product with a pleasing flavour and predictable nicotine strength. Without PG and VG, an e-liquid would be too strongly flavoured and would have too much nicotine to use safely.

PG and VG are also excellent emulsifiers. E-liquids often use several flavouring agents to create complex taste profiles. PG and VG help to keep the ingredients mixed so you have a consistent experience without needing to constantly shake the bottle to maintain even distribution.

What Is PG?

Propylene glycol -- food additive E1520 in the EU -- is an organic compound commonly synthesized from corn. In consumer products, PG is both an emulsifier and a preservative. You can find it in cosmetics and foods. In the United States, the Food and Drug Administration classifies PG as "Generally Regarded as Safe." Items classified as GRAS have been used as food additives since at least 1958 and are not known to be dangerous when ingested. Note, however, that the GRAS list only applies to items used for food purposes.

What Is VG?

Vegetable glycerin -- food additive E422 in the EU -- is a thick, slightly sweet liquid that is quite common because it occurs as a result of biodiesel production. Soybeans provide much of the world's VG. As a food additive, VG keeps products moist and soft because it attracts moisture. VG is also used as a sweetener. Like PG, the FDA in the United States considers VG GRAS.

What Are the Benefits of PG vs. VG?

Most e-liquids contain both PG and VG, so it isn't the presence of those liquids that affects your vaping experience -- it's the ratio.

PG:

• Has almost no flavour of its own and allows the flavour of an e-liquid to come through more clearly
• May enhance the throat hit of an e-liquid
• Is not very viscous, so it does not block the flow of e-liquid in smaller e-cigarettes
• Creates relatively small vapour clouds that dissipate quickly
• Vaporizes at a lower temperature than VG, making it appropriate for very small e-cigarettes
• May trigger allergies or sensitivities in a small percentage of people

VG:

• Has a slightly sweet flavour of its own and can make complex flavour profiles more difficult to discern -- manufacturers that use VG often compensate by using higher flavour concentrations
• Does not enhance the throat hit of an e-liquid
• Is very viscous and flows slowly through wick openings in smaller e-cigarettes
• Creates a full mouthfeel when vaporized
• Creates large vapour clouds that linger in the air for a while before dissipating
• Vaporizes at a higher temperature than PG, so it performs best in larger and more powerful e-cigarettes
• Is not known to trigger allergies or sensitivities

An e-liquid with a higher percentage of VG will have a full mouthfeel and will create large vapour clouds. The more VG an e-liquid contains, though, the more powerful an e-cigarette should be to vaporize the e-liquid effectively.

An e-liquid with a higher percentage of PG will work in any e-cigarette. It will feel thin and wispy in the mouth, and it will not create extremely large vapour clouds. However, the flavour notes in the e-liquid will be very clear and easy to discern.

Are PG and VG Safe?

PG and VG are common food additives. Both are considered safe to consume, but there have been no long-term evaluations on the safety of PG and VG for inhaling. Scientists are still working hard to determine the safety of e-cigarettes in general; it'll be a while before we know more about the safety of individual ingredients.

Are There Any PG-Only and VG-Only E-liquids?

PG-Only E-liquids

When the e-cigarette industry was new, the e-cigarettes that were available had very small heating coils that didn't generate much vapour per puff. With its low vaporization temperature, PG was the ideal base for e-liquids in those days. There was a time in which almost all e-liquids were PG-only. Today, though, PG-only e-liquids are rare because most people prefer the full mouthfeel and larger vapour clouds that VG provides. Virtually all e-liquids contain at least a little VG.

VG-Only E-liquids

VG as an e-liquid base has seen a steady increase in popularity over the years. As e-cigarettes become more powerful and more reliable, many people have come to prefer "Max VG" e-liquids for the larger vapour clouds that they generate. If you think that a "Max VG" or VG-only e-liquid might be the right choice for you, it's important to understand what the terms mean.

Max VG

The term "Max VG" has no standard definition in the vaping industry. For some manufacturers, the term may simply mean that the manufacturer used as much VG as possible without compromising the desired performance of the e-liquid. Some flavouring concentrates use PG as a base liquid. A manufacturer may use PG-based flavours but add only VG to the final e-liquid blend. Although you can be certain that a "Max VG" e-liquid contains a high percentage of VG, it is probable that the e-liquid will contain at least a small percentage of PG unless the manufacturer states otherwise. If you are sensitive or allergic to PG, you should avoid "Max VG" e-liquids unless you know how the manufacturer defines the term.

100 Percent VG or VG Only

A flavouring concentrate doesn't have to use PG as a base. Alcohol-based and glycerin-based flavours are also available. If a manufacturer makes an e-liquid using only VG and avoiding any PG-based flavours, the manufacturer can claim that the e-liquid is "100 Percent VG" or "VG Only." If you are allergic or sensitive to PG, this is the type of e-liquid that you should buy.

How Can I Tell If I Have a PG Allergy or Sensitivity?

If you have a PG allergy or sensitivity, it's likely that you already know. PG is so common in consumer products that you've likely encountered it already. Some of the symptoms that people with PG sensitivities have reported include coughing, hives, headaches, sore throats and rashes. If you experience any unpleasant symptoms when vaping, ask your doctor if you might have a PG sensitivity or allergy, and try a 100 percent VG e-liquid.

Want to learn more about e-cigarettes? Look at our E-liquid Buyer's Guide or read our E-cigarette Beginner's Guide.