Propanediol(in 14,641 products)
1. Emollient - Softens and soothes the skin. Helps with skin conditioning.
2. Emulsifier - Allows water and oils to remain mixed together to form an emulsion.
3. Humectant - Binds with water to increase skin hydration. Also enhances water absorption of the skin
4. Preservative - Prevents and inhibits the growth of unwanted microorganisms which may be harmful
5. Solvent (Cosmetics) - Enhances the properties of other ingredients
6. Viscosity Controlling Agent - Maintains or alters the thickness of a liquid, mostly used in cosmetics
Propanediol is a naturally derived ingredient that is commonly used in cosmetics and personal care products as a moisturizer, humectant, and emulsifier. It is also used in some food products as a solvent and preservative.
In cosmetics and personal care products, propanediol helps to hydrate and soothe the skin, leaving it feeling soft and supple. It also helps to improve the texture and consistency of products like lotions, creams, and shampoos.
Recent discoveries have shown that propanediol may have additional benefits for the skin. Studies have found that propanediol can help to improve the penetration of other skincare ingredients, allowing them to better reach the deeper layers of the skin where they can be more effective. It has also been found to have antimicrobial properties, which can help to reduce the growth of bacteria on the skin and prevent breakouts.
In food products, propanediol is used as a solvent and preservative. It is commonly found in baked goods, dairy products, and beverages.
Propanediol exists in two main chemical forms, 1,2-propanediol (also known as propylene glycol) and 1,3-propanediol. For the purposes of this research, propanediol refers to 1,3-propanediol.
Although propanediol has traditionally been processed and obtained from glycerol/glycerin, new studies have gone into making eco-friendly and renewable versions of propanediol. In research conducted by DuPont, propanediol polymer fibers can be made from corn sugar (Sorona®), which reduces greenhouse gas emissions by up to 40% and has similar fiber functionality compared to the petrochemical variant. 
It can also be made from enzymes and bacteria (such as Klebsiella, Clostridia and Citrobacter) and genetic engineering experimentation is underway to make the conversion to of biofuels to propanediol more efficient. 
DuPont has also made Zemea® for commercial purposes. It can be used as a humectant or emollient and “Zemea bio-derived 1,3-propanediol can replace petroleum-based glycols such as propylene glycol (PG), butylene glycol (BG) or glycerin.” and “Zemea propanediol is the world’s first 100% natural glycol alternative approved by ECOCERT and certified by the Natural Products Association”.  "In multiple studies using the modified Draize Repeated Insult Patch Test method, Zemea® propanediol produced no skin irritation, fatigue or sensitization—even at high concentrations." and "Researchers observed no clinically significant dermal irritation or allergic contact following exposure of up to 75% Zemea® propanediol at three different pH levels."  "Results from these studies show that Zemea® propanediol has low potential to irritate or sensitize human skin." 
Propanediol has a "widespread history of use for properties such as humectancy, moisturization or emulsification".  In animal studies conducted on rabbits (Draize method), propanediol has shown to be "mildly irritating". In guinea pigs, propanediol shows "no dermal irritation or sensitization".
An acute irritation dermal study was conducted on 40 healthy, Japanese volunteers and "no significant skin irritation was observed". It is generally presumed that propanediol shows a "lack of or low potential for dermal irritation and sensitization of skin". 
1. PubChem: https://pubchem.ncbi.nlm.nih.gov/compound/134919
2. A New Polymer Platform for the Future — Sorona® from Corn Derived 1,3-Propanediol. (J. Polym. Environ., 13(2), 159–167. doi:10.1007/s10924-005-2947-7)
3. Microbial production of 1,3-propanediol: Recent developments and emerging opportunities. (Biotechnol. Adv., 27(6), 895–913. doi: 10.1016/j.biotechadv.2009.07.003)
4. Natural glycol replacement for hair and skin care (https://pdfs.semanticscholar.org/12fb/9e52972759a624a130a8e965dc534b68dccf.pdf)
5. Zemea® Propanediol for Naturally Derived Personal Care Products (Cosmetics & Toiletries, May 2020)
6. Evaluating 1,3-Propanediol for Potential Skin Effects (Cosmetics & Toiletries, May 2013)