Don't take anymore! I ignored the first little bit of rash and wound up with it much more severely than if I hadn't done that (I thought it was a bug bite on my face).

Call your dr. first thing tomorrow but do not take any more until you are cleared. If the rash gets worse or spreads to your face monitor closely. If you have itching in your mouth or throat, swelling in your throat, any involvement of the eye or any difficulty breathing get to an ER (this is unlikely if it is on your arm and not your face but it is important if it spreads).

When I had it I had a little one night, just maybe an inch of itchy bumps; in the morning after I took another dose (stupid, stupid, stupid) of 150 or 200 mg I had it on my face and it kept spreading on my face for a day or two. In the end my entire face including lips and one eye were involved and I barely managed to avoid IV steroids. I truly believe it would have stopped if it weren't for that last dose.

Hyrdocortisone will help with the itching. If it gets bigger or the itching is worse than that you may need prescription steroid creams (I did). Avoid hot water on it as that tends to burn.

If you have any questions that I can answer please feel free to ask. I hope that it stops where it is for you and it should because you are much smarter than I was (and it's not on your face which is where you don't want it), but if you have questions I'm here.

Let us know what the dr says!