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 Propylparaben 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 Propylparaben near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About Propylparaben
It is a preservative that keeps a water-based product safe from microbes. A common paraben preservative rated 0/5.
Propylparaben in makeup and skincare
It sits near the end of the list in most water-containing makeup and skincare. Its irritancy is rated separately at 0/5, which is low.