The hand-washing episode illustrates a few important things about Tara and her father, Gene.

For Tara, it demonstrates just how isolated she is from the outside world. The issue isn't just that she doesn't choose do something so obvious and basic to most of us, it's that she isn't even aware of the strangeness of her behavior. She hasn't carefully weighed the options and chosen this approach—it simply doesn't occur to her that there might be another way of doing things. Not only is she so sheltered from outside influence that it takes until this point for her to know she's doing something unhygienic and unusual, it also takes this long for someone else to notice and speak up.

For Gene, this demonstrates several things: his commitment to shielding his kids from the outside world, his extraordinary psychological influence on his children, and especially his willful neglect of basic health and safety. His indifference toward basic health and safety, especially, turns out to be an ongoing threat to the Westover children. Most members of the family suffer serious injuries during the course of the memoir, and they have to contend with the difficult task of negotiating Gene's edicts and rules as they seek treatment and relief.

After Grandma-over-in-town passes, Tara comes to regret having let her father stand in the way of her relationship with her maternal grandparents and wishes she'd known her better.