How Do I Know If My Vegetable Glycerin (VG) or Propylene Glycol (PG) Has Gone Bad?

How Do I Know If My Vegetable Glycerin (VG) or Propylene Glycol (PG) Has Gone Bad?
Vegetable glycerin (VG) and propylene glycol (PG) are known for their long shelf life, but like any ingredient, they can eventually degrade or become unsuitable for use if stored incorrectly.
Knowing the signs of deterioration helps ensure you’re only using safe, high-quality products.
Will my VG and PG expire?
VG and PG don’t “spoil” in the traditional sense, but they can:
  • Degrade over time
  • Become contaminated
  • Lose their original quality

1. Check the Smell
Fresh VG and PG should have:
  • Little to no odour
  • A very mild, neutral scent
 If you notice:
  • A strong or unusual smell
  • A sour or chemical-like odour
This may indicate it’s no longer suitable for use.

2. Look at the Appearance
Both VG and PG should be:
  • Clear
  • Free from particles
Warning signs:
  • Cloudiness
  • Discolouration
  • Floating particles

3. Check the Consistency
  • VG is naturally thick and syrup-like
  • PG is thinner, similar to water
 If either becomes:
  • Unusually thick or thin
  • Sticky in an unusual way
It may have degraded or absorbed moisture.

 4. Check the Age
Even when stored properly:
  • Most products are best used within 1–2 years
Always check:
  • Batch dates
  • Manufacturer guidance

 5. Signs of Contamination
If the container has been:
  • Left open
  • Exposed to air frequently
There’s a higher risk of contamination.

When Not to Use It
Avoid using VG or PG if:
  • It smells off
  • It looks cloudy or discoloured
  • You’re unsure about its storage history

Conclusion
VG and PG are stable ingredients, but they aren’t indestructible. A quick check of smell, appearance, and consistency will help you decide whether your product is still safe to use.