What a 1/5 rating means
On the comedogenic scale, a 1 sits at the safe end of the scale — clogging is unlikely for most people. That places Zinc Oxide 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 Zinc Oxide near the end of a label is present in tiny amounts and matters far less than the same ingredient near the top.
About Zinc Oxide
It is a mineral-based ingredient, common in pigments and sun protection. A mineral sunscreen and soothing agent rated 1/5, generally friendly to acne-prone skin.
Zinc Oxide 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.