What is Ascorbic Acid?
Chemically, Ascorbic Acid is an active ingredient. Pure vitamin C, rated 0/5 for clogging. Can sting at high strengths but does not block pores.
You may see it on labels as Ascorbic Acid, L-Ascorbic Acid, Vitamin C, so it can hide under more than one name in an ingredient list.
Where Ascorbic Acid shows up
Ascorbic Acid is commonly formulated into targeted treatment products. Separately from clogging, its irritancy is rated 0/5 — low, so it's unlikely to sting or sensitise on its own.
Is Ascorbic Acid bad for acne-prone skin?
That low score makes Ascorbic Acid a reasonable choice even for acne-prone skin. As always, individual reactions vary, but it is not a likely cause of clogged pores.