User blog comment:Blood Reaper/Skyrim Dawnguard Trailer/@comment-3502822-20120601154436/@comment-67.81.147.191-20120602231226

The Falmer have spent thousands of year in dungeons and darkness, they most likely have no melanin content, meaning they could not withstand sunlight. So they would make common cause with the vampires, who suffer from this same problem.