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.
Propylene Glycol can be found in various common household items. Amongst others, these include:
- Nicotine inhalers
- Toothpaste and other oral hygiene products
- Medical products used orally, injected or as topical formulations
- Pet food
- Beauty products, including make-up, shampoo and baby wipes
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, there are two types of anti-freeze: toxic and “non-toxic”. The toxic anti-freeze uses the dangerous substance referred to as actually ethylene glycol, but it is not used in vaping. Typically PG-based anti-freeze is used in food-processing machinery where toxic anti-freeze could be problematic and is also sold at retail as “pet-safe” anti-freeze.
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.
Some people find a high level of PG irritating to the throat. True 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 may have a more common mild sensitivity to PG, and should look at using high-VG juice instead. Many vendors offer this 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.