[atalanta skye]

When someone pumps and experiences swelling, what does that swelling consist of?

[Babita]

Is it blood that fills the void created by the suction?

[blueheart]

No it shouldn't be blood. As I understand it, when the suction is applied it draws fluid from the body tissues, so the swelling is 99% water.

[Honey Fox]

Yes exactly, pumping for breast enhancement works by creating a vacuum which pulls fluid from the surrounding tissues and that buildup of fluid results in swelling. It's a simple process.