Face Covered in tiny whiteheads. :(

After a day in the sun my wife's face begins to itch at night, then she wakes up the next morning with her entire face covered in tiny white heads. The white heads clear up in about two days, and her face becomes very dry. It clears out completely in a week. She does clean her face as soon as she gets them and removes as many as possible.

Any idea what this could be ?