sudden forehead breakout - help!

mrs.mastro

I don't know where else to post this and I've not found the answer on Google, so I hope one of you ladies can help!  I normally have really clear skin, and very rarely get a breakout - maybe an occasional random pimple, but nothing major.  

We just went to Tucson on Sunday, and Monday morning I had this pimple-like rash on my entire forehead.  Tiny little whiteheads.  I treated them with salicylic acid, and they have been getting better each day since then, but the rash seems to be spreading down my nose and onto my cheeks now a bit.

I have no history of skin problems or acne.  I can't think of anything that would have caused an allergic reaction.  Does anyone have any idea what is going on??  Thanks!!