What is Propylene Glycol?
Chemically, Propylene Glycol is a humectant that draws water into the skin. A humectant and penetration enhancer rated 0/5 for clogging. Can be mildly irritating for some at high levels.
Where Propylene Glycol shows up
Propylene Glycol is commonly formulated into serums, toners, and moisturisers of every kind. Separately from clogging, its irritancy is rated 2/5 — low, so it's unlikely to sting or sensitise on its own.
Is Propylene Glycol bad for acne-prone skin?
Because it barely registers on the comedogenic scale, Propylene Glycol is generally a safe pick for breakout-prone skin and is often recommended as a gentler alternative to heavier ingredients.