Better Together campaigner Jim Murphy was pelted with eggs on Kirkcaldy High Street on Thursday afternoon.
The Labour MP for East Renfrewshire was in town as part of his 100 Days tour speaking to a boisterous crowd against independence.
Police Scotland were called after eggs were thrown Mr Murphy by a disgruntled member of the public, one of which hit the MP on the back of the head.
A police spokesman said: “Police were informed of a gathering at the Mercat, Kirkcaldy, and around 3.30 p.m. received a report of a disturbance where a number of eggs were thrown.
“Enquiries are ongoing into this matter.”