Why? The 13 year-old has a syndrome, appropriately called "hair brushing syndrome." The risk to her is that her brain might shut down because of static electricity, which is often generated when hair is brushed.
She also can't touch balloons, or wear shiny clothing. To get around this, she has to brush her hair upside down, and her hair hanging on the side of her bed, and her hair must be damp. They found this out one day when her mom was brushing her hair and she "flopped over and her lips turned blue," as her mother said.
What would you do if you couldn't brush your hair normally?