Propylene glycol is a clear, odourless, slightly thick liquid used as a humectant (moisture-holder) and solvent in cosmetics, soaps, hair care and many everyday formulations. In simple terms, it draws water to the skin and helps dissolve ingredients that don't mix easily, which makes it a workhorse ingredient for home and small-batch makers.
What is propylene glycol?
Propylene glycol is a synthetic organic compound with the chemical formula C3H8O2 and the IUPAC name propane-1,2-diol. Its INCI name on cosmetic labels is simply Propylene Glycol, and its CAS number is 57-55-6. It is produced from propylene oxide, which is hydrolysed to give a mix of glycols. The Azlok grade is an industrial-grade liquid at around 99% purity, with a specific gravity of about 1.036 and a boiling point near 188 °C. You may also see it listed under older names like methyl glycol or trimethyl glycol.
Common uses
Its two big strengths are holding moisture and dissolving things, so it turns up across a wide range of products:
- Skincare: a humectant in creams, lotions, serums and toners to keep the skin feeling hydrated and to stop formulas drying out.
- Soap making: especially in glycerin (melt-and-pour) soap bases, where it improves clarity and helps colours and fragrances disperse evenly.
- Hair care: shampoos, conditioners and leave-ins, where it aids spreadability and moisture retention.
- Colour cosmetics: a solvent that helps distribute pigments and keep the product smooth.
- General formulating: a carrier for fragrance oils, extracts and some active ingredients that need a helping hand to dissolve in water-based systems.
How to use it
Propylene glycol is water-soluble and easy to work with. A few practical pointers:
- Keep the dose modest. In most skincare and hair formulas it is used at low percentages of the total recipe, not as the main ingredient. More is not better; too much can leave a slightly tacky feel.
- Add it to the water phase. Because it mixes readily with water, stir it into the water portion of your emulsion before combining with the oil phase.
- Use it as a dispersing aid. For soap, blend your colour or fragrance into a little propylene glycol first, then add to the melted base for even results.
- Test small batches. Make a small trial batch, check the texture and feel, then scale up once you are happy.
Safety notes
This is an industrial-grade chemical, so handle it sensibly:
- Do not ingest it, and keep it away from children and pets.
- Work in a ventilated space and avoid splashing it into the eyes. Rinse with plenty of water if contact occurs.
- Always patch-test any finished cosmetic on the inner forearm before regular use, as some people are sensitive to it.
- Follow the MSDS and use tested, sensible concentrations rather than guessing.
- If you are formulating products for sale, confirm the grade suits your intended application and check the relevant COA and MSDS.
Buying and storage
Azlok stocks propylene glycol in sizes from a handy 100 gm all the way to 25 kg, so you can start with a small trial pack from around ₹149 and scale up for regular production. It is made in India and carries a shelf life of about 24 months.
Store it in a tightly closed container, away from direct sunlight and heat, in a cool, dry place. Keep it clearly labelled and separate from food items. Because it is hygroscopic (it attracts moisture), reseal the bottle promptly after each use to keep it in good condition.
FAQ
Is propylene glycol the same as glycerin?
No. Both are humectants used in cosmetics, but they are different compounds. Propylene glycol is thinner and a stronger solvent, while glycerin is thicker. Many makers use them together depending on the texture and performance they want.
Can I use propylene glycol in leave-on skincare?
Yes, it is widely used in creams, serums and toners as a humectant, typically at low percentages. Patch-test your finished product first, since a small number of people find it irritating.
Is propylene glycol water-soluble?
Yes. It mixes freely with water, which is why it is added to the water phase of emulsions and used to help disperse colours and fragrances.
Is the Azlok propylene glycol food grade?
The Azlok product listed here is industrial grade at around 99% purity. For any specific application, check the COA and MSDS and confirm the grade matches your intended use.
How should I store it and how long does it last?
Keep it in a sealed container in a cool, dry, shaded place. It has a shelf life of about 24 months when stored properly and kept away from moisture.