Dean was in a light sleep. His body never allowed his mind to get into a profound sleep. It was an instinct of his. Since the day he became a slave, he began to develop some traits that made him always wary of his surroundings even when doing these ordinary but necessary things.
When someone goes through the type of situation such as Dean went, they always develop this kind of danger sense. Traumatized people are generally warier of their surroundings and know how to read other people's intentions just by looking at their faces and seeing their actions. It became something natural.
Due to his light sleep, Dean's body could notice when something was coming near his cheek. It was a slow approach that sent chills all over his body as a result.
