What a 2/5 rating means
On the comedogenic scale, a 2 is still within the non-comedogenic range that dermatologists generally consider low-risk. That places Benzoic Acid 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 Benzoic Acid near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About Benzoic Acid
It is a preservative that keeps a water-based product safe from microbes. A common preservative rated 2/5 for clogging and 3/5 for irritancy.
Benzoic Acid 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 3/5, which is worth noting for sensitive or reactive skin.