What Causes Onion Odored Pus From Facial Acne?

Anytime I pop the pimples that appear on my face (especially the tiny blackheads on my nose), the pus smells exactly like raw onion. The smell seems rather strong to me and actually lingers on my fingers for a while afterward until I thoroughly wash my hands a couple of times. Granted, I occasionally eat a little bit of onion here or there (for example on a sandwich or in a soup or something), but I do not consume them in excess or anything like that, so I am very curious as to why the smell of onion is so strong in the pus! I cannot seem to find any helpful information at all on this matter from searching online myself, I a greatly appreciate your input. Thank you!!