What is D&C Red #9?
D&C Red #9 (INCI name: CI 15585:1) is a cosmetic colorant. A barium lake pigment used in colour cosmetics. Rated 1, grouping it with the low-risk reds rather than the 3-rated 17, 21 and 3.
You may see it on labels as D&C Red 9, D&C Red #9, D C Red 9, Ci 15585:1, so it can hide under more than one name in an ingredient list.
Where D&C Red #9 shows up
You'll most often find D&C Red #9 in lipsticks, blushes, and other colour cosmetics. Separately from clogging, its irritancy is rated 0/5 — low, so it's unlikely to sting or sensitise on its own.
Is D&C Red #9 bad for acne-prone skin?
That low score makes D&C Red #9 a reasonable choice even for acne-prone skin. As always, individual reactions vary, but it is not a likely cause of clogged pores.