An individual whose face is not identical on the right and left sides is said to possess facial asymmetry. This can come from many different sources, ranging from asymmetrical freckles or parted hair to serious facial deformities, such as those caused by physical harm or birth defects. Physically, possessing perfect symmetry does not tend to significantly influence one’s health or functionality. Studies have suggested, however, that asymmetry may have a significant effect on interpersonal relationships. People tend to subconsciously interpret symmetry and asymmetry in different individuals as an indicator of one’s general level of health and attractiveness.
Fluctuating asymmetry is a term used to describe variance in the body’s normal bilateral symmetry that occurs over the course of one’s life. Fluctuating asymmetry is one of the primary causes of facial asymmetry, but it also applies to other bodily traits that normally exhibit bilateral symmetry, such as the lengths of fingers on one’s right and left hands. It is believed that fluctuating asymmetry occurs when one’s genome is not fully able to produce and maintain completely ideal traits in unstable and often non-ideal environmental conditions. Based on this notion, one may interpret facial asymmetry as a sign of poor genetic ability to handle environmental strain.

It should be noted that true facial symmetry is extraordinarily rare and almost never occurs. Differences in hair patterning and teeth, minor skin imperfections, and even slight variation in bone structure are quite common. These differences tend to be either too small or too ordinary to be considered particularly significant.
Facial asymmetry is considered to be important largely because of its impact on attraction and interpersonal relationships. One may, for example, subconsciously perceive facial asymmetry resulting from fluctuating asymmetry as a sign that one is genetically unable to successfully cope with environmental conditions. This perception may influence how attractive someone finds a potential mate to be.
Fluctuating asymmetry is by no means the only possible cause of facial asymmetry. Significant injuries to the face or head can alter bone structure, damage teeth, or leave scars that cause visible asymmetry. Misalignments of the jaw can also lead to visible facial asymmetry. Even if it is not caused by environmental factors, asymmetry of any kind can suggest poor health or a weak genetic makeup, particularly to potential mates. It is possible to correct some forms of asymmetry through various forms of plastic surgery, skin treatment, and tooth and jaw treatment.