Propanediol in Hair Products: What It Is and What Safety Reviews Show
"Propanediol" covers several related cosmetic ingredients, usually used as solvents or pH adjusters, not as hair-growth ingredients. We found no study of propanediol on hair. The research is on safety, and the reports we found concern related compounds: an alkane diol panel review, a toxicology review of 2-methyl-1,3-propanediol, and a review of aminomethyl propanediol.
Here's what those safety reviews say.
I LOVE MY HAIR NOW
FullyVital hair serum and hair vitamins made tremendous improvements in my hair. I truly love my hair now.
Dorit S., 
Key Takeaways
- Alkane diols such as propanediol are mostly used in cosmetics as solvents. An expert panel found seven of ten alkane diols safe at present use levels, and said data were insufficient for three.
- 2-methyl-1,3-propanediol had low toxicity, barely perceptible skin irritation in human volunteers and minimal response in about 1% of people in patch tests.
- Aminomethyl propanediol, used as a pH adjuster in cosmetics, was judged safe in cosmetics at present use levels.
- We found no study of any propanediol for hair growth.
What Is Propanediol?
Propanediol is a small diol (a type of alcohol). Different propanediols have different jobs in cosmetics, from solvent to pH adjuster, and safety assessments are done compound by compound.
Does Propanediol Help Hair?
It isn't a hair-growth ingredient. If you see it on a label, it is a formulation ingredient.
If A Product Irritates You
- Stop using it and see a dermatologist if the reaction persists.
- Patch test new scalp products.
What The Research Shows
Alkane Diols In Cosmetics
The Expert Panel for Cosmetic Ingredient Safety assessed 10 alkane diol ingredients that are structurally related small diols, most reported to function as solvents in cosmetics. It concluded seven are safe in present practices of use and concentration, and that data were insufficient for three: 1,4-butanediol, 2,3-butanediol and octanediol (Scott et al., 2024). The abstract doesn't list which seven.
2-Methyl-1,3-Propanediol
A toxicology review of 2-methyl-1,3-propanediol found low toxicity by all routes. It is rapidly absorbed through skin and by mouth and excreted in urine. Barely perceptible skin irritation was seen in human volunteers, and patch tests showed minimal response in about 1% of individuals. A 90-day rat study found no adverse effects (Fowles et al., 2017).
Aminomethyl Propanediol
The Cosmetic Ingredient Review panel assessed tromethamine, aminomethyl propanediol and aminoethyl propanediol, which function in cosmetics as pH adjusters. It concluded they are safe in cosmetics in the practices of use and concentration given in the assessment (Becker et al., 2018).
Caprylhydroxamic acid is another cosmetic ingredient with a safety literature of its own; see caprylhydroxamic acid.
See also: Lecithin for Hair: What the Research Shows · Polysorbate 80 in Hair Products: What It Is and What the Research Shows
Propanediol is one of the ingredients in FullyVital's Hair Revival Serum. For how the evidence for each ingredient in the line stacks up, see our evidence-tier breakdown.
Frequently Asked Questions
Does propanediol help hair growth?
We found no study showing that it does.
Is propanediol safe?
Related compounds were judged safe at present use levels in safety reviews. Patch test new products.
What is propanediol used for in hair products?
Most reports describe diols as solvents, and aminomethyl propanediol as a pH adjuster.
References
- Scott LN, Fiume M, Bergfeld WF, et al. Safety Assessment of Alkane Diols as Used in Cosmetics. Int J Toxicol. 2024. PubMed
- Fowles J, Lewis C, Rushton E. Studies on the environmental fate, ecotoxicology and toxicology of 2-methyl 1,3-propanediol. Regul Toxicol Pharmacol. 2017. PubMed
- Becker LC, Bergfeld WF, Belsito DV, et al. Safety Assessment of Tromethamine, Aminomethyl Propanediol, and Aminoethyl Propanediol as Used in Cosmetics. Int J Toxicol. 2018. PubMed
Discover the Power of Fully Vital Hair Growth ProductsAt Fully Vital, we have developed a range of hair growth products that are designed to address the specific needs of aging hair. Our products have been formulated using powerful, science-backed ingredients that have been shown to slow down and even reverse the signs of aging in hair. Here are some key features and benefits of our products:
If you are ready to experience the benefits of our hair growth products, why not give them a try today? Take the first step towards healthier, more youthful-looking hair with Fully Vital. |
Read more
Ethoxydiglycol: A Powerful Ingredient for Hair Regrowth and Combating Grey Hair
Discover the Power of Ethoxydiglycol for Hair Regrowth | Fully Vital Curious about ethoxydiglycol? Learn how this natural compound stimulates hair regrowth and combats graying hair. Explore our Veg...
Read more
Fine Hair: What It Is and What Changes With Age
What research says fine hair is, how hair diameter and density change with age in women, and how thin hairs differ structurally.
Read more
