The idiom walking on eggshells generally describes a situation in which people must tread lightly around a sensitive topic, or make every effort not to offend a volatile or hypersensitive person. Literally walking on the empty shells of eggs would require exceptional caution and self-control, similar to the feeling of avoiding conflict with an easily disturbed friend, relative or employer. Family members of active alcoholics or rageaholics often use this phrase to describe their careful avoidance of conflict with their loved one.
The origin of the idiom is a matter of dispute, but the general consensus is that walking on eggshells came from the same place as other cautionary actions, such as walking on thin ice or broken glass. Some sources suggest that it came from an earlier idiom, "walking on eggs." While walking on eggshells presents enough difficulty for most people, walking on the whole egg without damage would be nearly impossible. Certain politicians who took extraordinarily cautious positions on an issue were said to have the dubious ability to walk on eggs without breaking them.
There are any number of people who have poor anger management skills or a hair trigger temper. Even the slightest offense or deviation from routine may be enough to trigger an explosive emotional outburst or physical reaction. This volatility may be enough to cause others to modify their own behavior and actions to maintain a tense but workable work or social environment. Walking on eggshells around a known rageaholic or temperamental person may be viewed as a form of self-preservation, although often accompanied by feelings of anxiety or dread. Failure to maintain such a non-confrontational atmosphere may end badly.
There are also times when people may feel like walking on eggshells around otherwise self-controlled family members, co-workers or employers. A certain subject may prove so potentially upsetting that others agree not to bring it up around those it affects most. Family members may be extra cautious around a patient until the results of an important medical test are revealed, for example. Employees may feel as if they were walking on eggshells until their employer learns of a project's fate. Any circumstance in which the need for diplomacy and tact outweigh the need for direct confrontation could easily trigger a need to tread lightly. Once the situation has been resolved or the person's own coping skills improve, such careful action may no longer be required.