She’s soaking in a hot tub to quiet her nerves. She’s terribly upset.

– Tennessee Williams

A Streetcar Named Desire, Scene 1. Stella tells Stanley and Stella that Blanche is having a hot bath to soothe her "nerves." This is the first of a number of baths Blanche takes in the play. She feels the need to constantly physically clean herself. But she also wants to cleanse herself of past sins we later learn about – guilt over her husband’s suicide, a promiscuous past and affair with a teenage student while she was his teacher. Her compulsive bathing is akin to the mad Lady Macbeth’s attempts to wash Duncan’s imaginary blood off her hands after his murder: "Out, damned spot! out, I say!" The fact that Blanche must take a bath to quieten her nerves suggests a mental vulnerability that will ultimately lead to her madness.