Under-eye bags is a common term for bulges beneath the eyes. Displacement of existing fat, together with reduced tissue support, often plays a part. These bags should be distinguished from the anatomical lacrimal sacs that form part of the tear drainage system.
Not every swelling of the lower eyelid has the same cause. Fluid retention, allergies and other conditions can look similar. New, one-sided or painful swelling should be assessed medically.
When the findings are suitable, lower eyelid surgery can redistribute or reduce fat and adjust other structures. It cannot reliably prevent later changes. Fillers are not automatically a suitable alternative for someone who already tends to develop swelling.