How To Cure Rashes Behind Ear And Neck?

Hello - my 14 yr old daughter showed me a rash that was directly behind her ear yesterday. It had bumps about the size of a pea in circum. and smaller...raised, red, not painful or itchy. Today, the rash has spread down her neck, around the bottom of her hairline and up into her hair. It's itchy and after I put Neosporin on it, it began to itch even more and became painful. No other pain, no fever, but has been more tired than usual. However, she started her period today so the fatigue was prob from PMS. Any clue as to what this virus is?