What a 0/5 rating means
On the comedogenic scale, a 0 means it will not clog pores for essentially anyone, including very acne-prone skin. That places Mineral Oil in the range most people, including many with acne-prone skin, tolerate well.
One thing the number cannot tell you is concentration. Ingredients are listed in descending order, so Mineral Oil near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About Mineral Oil
It is an occlusive that forms a breathable seal to slow water loss. Cosmetic-grade mineral oil is inert and rated 0-1. Because it contains no fatty acids, it is one of the few occlusives considered safe for fungal acne.
On a label it can read as Mineral Oil, Paraffinum Liquidum, Liquid Paraffin, Parrafin — worth knowing when you scan an ingredient deck.
Mineral Oil in makeup and skincare
It anchors heavy balms, some full-coverage sticks, and night creams. Its irritancy is rated separately at 0/5, which is low.