Stearic Acid
In plain terms
A waxy fatty acid found in plant and animal fats and in your own skin barrier. It softens skin, thickens creams, and helps oil and water mix. Well tolerated and low on the pore-clogging scale.
What the evidence shows
Stearic acid is a saturated long-chain fatty acid, the same type that forms part of the skin's own barrier lipids, and it is drawn from sources like shea butter, cocoa butter, coconut, and other vegetable or animal fats. In products it softens skin, thickens and stabilizes creams, and works as a co-emulsifier so oil and water stay blended. Its safety record is strong: the CIR panel rates it safe as used, it carries a low hazard rating, it is neither a sensitizer nor a photosensitizer, and the FDA lists it as generally recognized as safe in food. Its comedogenic rating is low, so for most people it does not clog pores, and research on skin lipids shows that adding fatty acids like stearic acid back into cleansers helps preserve the barrier and reduce water loss. Two small notes round it out. In pure, concentrated form the raw material can irritate skin, eyes, and airways, but that applies to handling the neat ingredient, not the low levels in a finished cream. And because free fatty acids can feed the yeast involved in fungal acne, people prone to that may prefer to limit it. For nearly everyone it is a gentle, barrier-supporting workhorse.
On the label
Listed as stearic acid or octadecanoic acid. No real catch for most skin types. If you deal with fungal acne, the small itchy bumps that resist normal acne treatment, free fatty acids like this one can be a trigger, so you may want to limit it.