Getting "egged" can cause serious damage, according to research.
Politicians, like Ruth Kelly, have been the victims of egg attacks
A Liverpool-based study found that being pelted by a raw egg may result in eye injury - and could even lead to blindness.
The researchers warn that egg hurling, sometimes used as a form of protest or prank, is far from harmless.
They point out, in the Emergency Medical Journal, that an egg has the same dimensions as a squash ball but carries even more weight when lobbed.
Researchers from Royal Liverpool University Hospital looked at the records of 18,651 patients who had attended an eye unit over a 14-month period.
They discovered that 13 people had been the victims of an egg attack.
Many of these cases were clustered around Halloween, and 12 of the patients were men.
Eight had serious injuries to their eyes, including detachment of the retina, macular damage and raised internal pressure, which can lead to a permanent loss of eyesight.
While most recovered, one of the patients, who had been hit from an egg thrown from a passing car, suffered permanent damage to his eye.
The other patients sustained moderate or minor eye injury.
'The perfect instrument'
Jon Durnian, lead author of the paper from the Royal Liverpool University Hospital, said: "The shape and weight of an egg makes it a perfect instrument to cause quite a lot of damage if it is thrown accurately.
"Here, we have shown that serious injury can happen - it can deform the eye quite substantially and even lead to blindness."
Mr Durnian said the public should be made aware of the damage an egg can cause and that throwing eggs should definitely not be encouraged.
He particularly criticised the sale of eggs marketed specifically for lobbing, including Mischief Eggs, sold during Halloween 2004 by supermarket Asda.
Larry Benjamin, from the Royal College of Ophthalmologists, said: "If the egg doesn't break on impact, I imagine that its is like being hit by a heavy stone.
"Most people would imagine an egg would break quite easily against the bones of the skull, but if the point lands on the eye, it could cause huge damage."