Why does someones hair stand on end when they are touching a charging van de Graaff generator?

When someone touches a Van de Graaff generator, it accumulates a high voltage of static electricity. This causes the person's body to become electrically charged, creating a repulsive force between the hairs on their head, which are also charged. As like charges repel, the individual hairs stand on end, creating the characteristic "hair-raising" effect. This phenomenon is a visual demonstration of static electricity in action.