Genetics
Swollen eyelids or puffy eyes can also be an inherited trait or a product of genetics. An example would be eye allergies, one of the most common causative conditions of swollen eyelids, which can be inherited among family members. Other inherited medical conditions like thyroid problems may also cause swollen eyelids.
Genetics can also cause the weakening of the tissues and the thin and delicate skin, and other supporting structures around the eyes. Deterioration of the tissues in the eye area can also cause darkening under the eyes. Likewise, it can cause fat to move into the lower eyelids, which could make them look swollen. In some cases, weakened eye tissues and dark under eyes can also lead to fluid buildup, causing them to appear puffy.
Another genetically-linked theory says that swollen eyelids are associated with fat cell regeneration. When the stem cells in the under-eye create more new fat faster than the pre-programmed cell death can reduce the amount of fat, swollen eyelids may appear. In some cases, older fat cells swell beyond average size while the fat cell population remains the same, giving off the same results.
