I am sharing my current medical situation in hopes it may save you from my experience.
If you get a rash that is unusually painful for its appearance, see your doctor as soon as possible. If could be a staph infection.
I developed a rash on my forehead last week. It looked just like poison oak, which I get often, and I was treating it with a steroid cream. By the second day, the rash started to be painful. The following morning, the rash began to darken, turning black by noon. I called the doctor and got an appointment for the next morning.
By the time I saw the doctor at 9 AM the next morning, The black rash was an open sore, roughly an inch long and 3/4 inch wide, with a 2 inch red, hot, swollen raised border. The swelling extended down the left side of my face to the neck.
The doctor started me on a combination of oral antibiotics. He told me that there is a possibility that the staph may not respond to the drugs and them we move to some really nasty medication. I am on day 3 with no noticable healing but at least they are not getting worse. The antibiotics make me feel pretty bad.
Staph is bad--don't hesitate to see your doctor ASAP