Shireen was one of the shows truly good and innocent characters, so naturally, bad things happened to her. It is revealed that she contracted greyscale as an infant. As mentioned above, the childs version is the mildest and most treatable, though it is still often lethal since most people will not have access to the measures necessary for preventing the disease from spreading. It helped that Shireens father was a rather notable (and noble) Baratheon. After she caught the disease from a Dornish doll, Stannis was encouraged to send her across the Narrow Sea to live out what remained of her life with the Stone Men. Refusing to give up on his daughter (how times would change...), and as he revealed in Season 5 Episode 4, Sons Of The Harpy, he called in every Maester on this side of the world, every healer, every apothecary in order to save her. She was left with a permanently scarred face, and a mother who completely resented her, but she survived thanks to her powerful father. Treatments are said to include limes, mustard poultices and scalding-hot baths, as well as prayer and fasting. The exact combination used on Shireen is unclear, but the methods worked, although most people who contract the disease arent so lucky.