Propanediol
Propanediol · INCI Propanediol
Some ingredients you choose. Some arrive because they came in the bottle with something else. Propanediol is the second kind. It is part of our chlorella active, where it dissolves the algal extract and helps keep it stable.
Made by fermentation, and a different molecule from propylene glycol. It is a humectant too, though at this level glycerin does most of that work.
What it is
Propanediol is a clear liquid made by fermentation. It is in our formulas because our chlorella active is supplied as a liquid, and propanediol is about a third of that liquid. It dissolves the algal extract and helps keep it stable and free of microbes. Take it away and there is no chlorella to add.
It is also a humectant, which means it attracts water and holds on to it, in much the same way glycerin does but with a lighter feel. At about a third of the 1 percent chlorella active, its share of that work is small beside the glycerin.
Its name is close to propylene glycol, and the two are often muddled. They are different molecules.
What it does in our formulas
Propanediol dissolves and stabilises our chlorella active, and it is a humectant in its own right.
It carries the chlorella
This is why it is in the formula. Our chlorella active is supplied as a liquid, and propanediol is about a third of it. It dissolves the algal extract and helps keep it stable and free of microbes before the active reaches our workshop.
Well characterisedIt is also a humectant
Propanediol attracts water and holds on to it, as glycerin does, with a lighter and less tacky feel. It arrives only as part of the chlorella active, so its share of that work is small beside the glycerin.
Well characterisedWhat the research does not show
Propanediol is often mistaken for propylene glycol, and it is sometimes sold as a microbiome-friendly preservative.
Marketed as A harsh synthetic chemical, or the same thing as propylene glycol
Marketed as A microbiome-friendly preservative
On the label and in the range
Propanediol appears in every one of our formulations at around three tenths of a percent, which is why it sits where it does in the list, above the chlorella it arrives with. About a third of our chlorella active is propanediol, and every part of that active is declared. The exact percentage is published on each product page.
Is it suitable for me?
Propanediol has a good safety record and is well tolerated on sensitive skin. Within our chlorella active it is certified vegan by the Vegan Society and approved under the COSMOS and NATRUE organic standards. It is made by fermentation rather than from petroleum, and it carries no restrictions under UK or EU cosmetic law.
As with anything new, if your skin reacts easily it is worth patch testing first.
The research behind this page
We review the published literature. We do not conduct the studies below.
- ALGAKTIV S.L. (Barcelona). ALGAKTIV BioSKN Product Information Dossier, v2024.0, and technical efficacy dossier. Manufacturer data, unpublished. Sponsor-generated. →
- Scott LN, Fiume M, Bergfeld WF, et al. Safety Assessment of Alkane Diols as Used in Cosmetics. Int J Toxicol 2024;43(2 Suppl):70S-131S. →
- Pinto D, Ciardiello T, Franzoni M, Pasini F, Giuliani G, Rinaldi F. Effect of commonly used cosmetic preservatives on skin resident microflora dynamics. Sci Rep 2021;11:8695. (Industry-funded; peer-reviewed.) →