Bloom is also the very very thin and transparent coating over the outside of an eggshell that protects the pores. It is also called the egg's cuticle. It keeps the egg from drying out, and keeps bacteria from getting in. It also keeps the yolk and the white of the egg from being contaminated by any flavors or odors in the external environment.

Eggs are washed before they are sent to your local market; this takes off the chicken poo, but it also takes off the bloom. Egg packers will often give eggs a light coating of mineral oil, as an artificial bloom.