There are very few places in the world that are naturally germ-free, but eggs from a healthy bird are one of them.  Ingraham says they stay that way because of their chemical defenses. Bacteria may get through a crack in the shell and the membrane underneath, but then the egg white fights back. In the egg white, there are three proteins that are very effective at combating bacteria.

One of these is called lysozyme. It isn't just in egg whites — it's also in tears, saliva and the drippy stuff that comes out of your nose. In fact, that's how it was discovered by Alexander Fleming (who also discovered penicillin) — Fleming happened to notice that when drips from his nose fell onto certain bacteria, they died.

It's a pretty neat trick. Lysozyme breaks the wall of the bacteria. And since bacteria are under pressure — like a balloon — if you break the wall, they explode. Lysozyme doesn't work on everything, but it can pop a lot of bacteria.

But the egg has two other ways to kill invaders. One is a protein that prevents bacteria from getting an essential vitamin that they need. The other is called conalbumin, and it's this protein keeps bacteria from getting the iron they need to grow.

 Thanks Off the Food Grid