""We’re just gonna let Madam Marsh off first, though -" there was more retching from downstairs, followed by a horrible spattering sound "- she’s not feeling ‘er best.""
Stanley Shunpike describes a particularly violent case of motion sickness suffered by Madam Marsh on the Knight Bus[src]

Motion sickness is an aliment caused by a disagreement with how the body visually perceives movement and how the inner ear senses it. Motion sickness often causes dizziness, fatigue, and nausea, and can lead to vomiting in extreme cases. A magical variant of motion sickness is Portkey-sickness, which specifically triggers upon travel by Portkey.

Madam Marsh suffered from a severe case of motion sickness. Despite this, for whatever reason, she was a frequent traveller on the Knight Bus, and often suffered greatly during the journey to her destination.

A Hogwarts School of Witchcraft and Wizardry student once wondered allowed if the travel to Hogwarts Castle on the Hogwarts Express would give them motion sickness.[1]


Notes and references