What is D&C Red #7?
Chemically, D&C Red #7 (INCI name: CI 15850:1) is a cosmetic colorant. The calcium lake of D&C Red #6, one of the most common lipstick pigments in use. Rated 1, so the pigment itself is a low-risk component of a lip or cheek formula.
You may see it on labels as D&C Red 7, D&C Red #7, D C Red 7, Ci 15850:1, so it can hide under more than one name in an ingredient list.
Where D&C Red #7 shows up
D&C Red #7 is commonly formulated into 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 #7 bad for acne-prone skin?
That low score makes D&C Red #7 a reasonable choice even for acne-prone skin. As always, individual reactions vary, but it is not a likely cause of clogged pores.