What makes Sandy so sick at the sleepover in "Grease"?

Sandy gets sick at the sleepover after getting her ears pierced. In "Grease," Frenchy pierces Sandy’s ear, and Sandy reacts badly when she sees the blood.

The scene takes place at the pajama party hosted by the Pink Ladies. Sandy is uncomfortable with several of the group’s experiments, including smoking a cigarette and drinking wine, but the ear-piercing attempt produces the most dramatic reaction. The sight of blood makes her feel faint and ill, highlighting how sheltered she is compared with the other girls.

The moment also helps establish the social pressure surrounding Sandy. Rizzo and the other Pink Ladies tease her for being innocent and old-fashioned, while Frenchy tries to help her fit in. Sandy’s discomfort contrasts with the tougher image she adopts later in the film.

Some summaries mention the cigarette and wine as additional reasons she feels unwell, so the scene can be remembered as a combination of failed attempts to fit in. However, the clearest plot answer is the ear piercing—especially her reaction to seeing blood after Frenchy performs it.