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 Kaolin 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 Kaolin near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About Kaolin
It is a mineral-based ingredient, common in pigments and sun protection. A mild absorbent clay rated 0/5, often used in masks for oily skin.
On a label it can read as Kaolin, Kaolin Clay, White Clay — worth knowing when you scan an ingredient deck.
Kaolin in makeup and skincare
It is central to mineral makeup, pressed powders, and mineral sunscreens. Its irritancy is rated separately at 0/5, which is low.