I had one from a spider bite on my torso,
this was before the huge wave of staph that hit after the hurricane.
Had no idea what it was, swelled up and literally looked like a gun-shot wound about 4 days later.. sadly one of my relatives passed at the same time so I didn't want to complain.
The blackness was over the size of my fist, i to cut my pants/boxers just to lay down.
I have no idea how I let it get that bad, it was just 2 days or so.. then I couldn't speak properly and my tongue was swelling.
At that point I went into the bathroom, and put boiling hot water on it and lanced it.. at which point I blacked out from the pain and came 2 inches to knocking my head open on the bathtub.
It started to look a tiny bit better, but after I showed it to someone that immediately said "what the fuck, go to the hospital" so I did.. ended up getting bactrum ointment and bactrum antiobiotics.. and damn those are rough on your stomach
I WOULD ADVISE YOU TO ALWAYS HAVE SOME BACTRUM LOTION AND ANTIBIOTIC AROUND WHEN YOU CAN, BECAUSE THAT IS ALL A DOCTOR WILL DO FOR YOU.
Also it's not always about hygene, spider bites/insect bites can cause it as well.