Where propylene glycol sits in the Sniff System
propylene glycol is a flagged ingredient in the Sniff Controversial Ingredient Penalty list. Products that include it incur a methodology-specified penalty. The penalty is documented, versioned, and challengeable through the corrections process.
Every methodology choice is published, citeable, and subject to revision when new evidence arrives. Read the full Sniff methodology for the formulas behind every score component, or file a correction if you think this position is wrong.
Similar ingredients in the catalog
Sniff's semantic graph clusters these ingredients near propylene glycol by formulation profile. Each links to its own ingredient page.