Bags under your eyes form when small pads of fat that normally sit deep inside your eye socket push forward against the skin. This happens because the thin membrane holding that fat in place weakens over time, and the bone structure around your eye gradually shifts. The result is that soft, puffy bulge just below your lower lashes that can make you look tired even when you’re not.
The Anatomy Behind Under-Eye Bags
Your eye sits cushioned inside the skull on small pockets of fat. These fat pads are held in place by a thin, fibrous wall called the orbital septum, which acts like a retaining barrier between the fat and the surface of your lower eyelid. When this barrier is strong, the fat stays tucked behind it. When it weakens or stretches, the fat herniates forward, creating visible bulges beneath the skin.
The skin on your lower eyelid is some of the thinnest on your entire body. There’s very little subcutaneous tissue to hide what’s happening underneath. So even a small amount of fat displacement becomes visible almost immediately, in a way it wouldn’t on, say, your cheek or forehead.
Why Aging Is the Primary Cause
Several structural changes happen simultaneously as you age, and they compound each other. The orbital septum loses its tension. The ring-shaped muscle around your eye (the one you use to blink and squint) loses tone and thins out. The skin itself loses elasticity. Any one of these changes alone might not create noticeable bags, but together they allow the orbital fat to slide forward with little resistance.
What makes this worse is that the bone itself changes shape. The inferior orbital rim, the bony ledge that forms the bottom edge of your eye socket, drifts downward and backward with age. This stretches the ligaments and soft tissues that are anchored to it, including the orbital septum and a structure called the tear trough ligament. As these attachments get pulled taut and then loosened, the fat pads lose their structural support. Research from a 2017 study in the Journal of Plastic, Reconstructive & Aesthetic Surgery described this bony remodeling as “a major cause of age-related intraorbital fat herniation,” noting that mechanical stretching of the lower eyelid combines with muscle and tissue atrophy to produce the characteristic droop.
There’s also the tear trough itself to consider. This is the groove that runs from the inner corner of your eye down toward your cheek. A ligament anchors the skin into the bone along this line. As the ligament weakens and the fat pads above it descend, the contrast between the puffy bag and the hollow groove beneath it becomes more pronounced. Your bone structure plays a role here too: people whose cheekbones sit further back tend to have a deeper tear trough, which makes any fat herniation look more dramatic.
Temporary Bags From Fluid Retention
Not all under-eye puffiness comes from fat displacement. A lot of what people notice in the morning is fluid buildup in the loose tissue beneath the skin. When you sleep, you’re horizontal for hours, and gravity distributes fluid more evenly across your face instead of pulling it downward. The tissue around your eyes, being so loose and thin, absorbs that fluid readily.
Sleep deprivation makes this worse because your body retains more fluid when you’re underslept. High sodium intake has a similar effect: excess salt causes your tissues to hold onto water, and the under-eye area shows it first because there’s so little structural resistance. Allergies are another common trigger. Histamine release increases blood flow and fluid leakage from small vessels around the eyes, producing that swollen, slightly reddened look.
These fluid-driven bags are different from age-related fat herniation in one important way: they’re reversible. A cold compress constricts blood vessels and reduces fluid accumulation. Sleeping with your head slightly elevated helps gravity drain fluid away from the eye area overnight. Cutting back on salt, managing allergies, and getting adequate sleep can all reduce morning puffiness noticeably within days.
Bags vs. Festoons
It’s worth knowing the difference between standard under-eye bags and a related but distinct condition called festoons, or malar mounds. Under-eye bags sit directly below the lash line and are caused by fat pushing forward. They feel firm when you press on them and can’t be easily shifted side to side. They also become more prominent when you look upward, because that movement pushes the orbital fat further against the weakened septum.
Festoons, by contrast, sit lower on the cheek. They’re caused primarily by sun damage to the skin and the effects of opposing muscle forces over decades. They feel squishy, can be moved side to side with a finger, and don’t change much when you shift your gaze upward. The distinction matters because the two conditions respond to different treatments.
What Determines How Severe Yours Are
Genetics set the baseline. The thickness of your orbital septum, the depth of your eye socket, the position of your cheekbones, and how much orbital fat you carry are all inherited traits. Some people develop visible bags in their 30s; others never develop prominent ones. If your parents had noticeable under-eye bags, you’re more likely to as well.
Beyond genetics, the main accelerating factors are sun exposure (which breaks down collagen and elastin in the already-thin eyelid skin), obesity (which increases the volume of orbital fat), thyroid conditions (which can cause fat to expand within the orbit), and smoking (which speeds up the loss of skin elasticity). Trauma or prior eye surgery can also weaken the orbital septum directly, allowing fat to herniate earlier than it otherwise would.
How Under-Eye Bags Are Treated
For temporary, fluid-related puffiness, topical products containing caffeine can help by constricting blood vessels near the skin’s surface. Cold compresses work on the same principle. Lymphatic drainage massage, where you gently press and sweep the tissue from the inner corner of the eye outward and downward, can help move trapped fluid back into circulation. These approaches won’t do much for bags caused by fat herniation, though.
For structural bags, the main option is a surgical procedure called lower blepharoplasty. Modern techniques have moved away from simply removing the protruding fat, which can leave the under-eye area looking hollow. Instead, surgeons now often reposition the fat, draping it over the orbital rim to fill in the tear trough and create a smoother transition between the lower eyelid and the cheek. The medial and central fat pockets are released and sutured into a new position along the tear trough line. The lateral fat pad may be partially removed if needed.
Injectable fillers offer a non-surgical alternative for milder cases. By adding volume to the tear trough below the bag, fillers can reduce the contrast between the puffy area and the hollow groove, making bags less visible without addressing the fat itself. This is a temporary fix, typically lasting 6 to 18 months, and carries its own risks in such a delicate area.