Tory leader David Cameron has joked that it was the "first of the campaign" after he was hit by an egg during a visit to a college in Cornwall.
Mr Cameron was struck on the shoulder as he emerged from answering students' questions at Cornwall College Saltash.
Eyewitness said the young man who threw the egg was immediately led away.
Mr Cameron, who was confronted by a giant chicken on Tuesday, joked afterwards: "Now I know which came first - the chicken not the egg."
The egg was thrown by a student who was inside the building as Mr Cameron was about to walk out.
It glanced off his shoulder and splattered on the jacket of a police officer beside him.
The yoke also stained Mr Cameron's white shirt.
The student was arrested and then quickly released after police established he did not have any more missiles with him, a Tory aide said.
A spokesman for Devon and Cornwall Police said: "It was a 16-year-old student that threw an egg.
"It didn't hit David Cameron but it hit someone else at the event. He was arrested but was de-arrested before reaching a police station."