Redness isolated to the bottom half of your eye is usually caused by one of a handful of common conditions, most of them minor. The lower portion of the eye is more exposed to air, allergens, and dryness than the upper portion (which stays partially protected under the upper eyelid), so it tends to show irritation first. The most likely explanations range from a burst blood vessel to dry eye, allergies, or eyelid inflammation.
A Burst Blood Vessel
If the redness appeared suddenly as a bright, well-defined red patch, you’re probably looking at a subconjunctival hemorrhage. This is a small bleed beneath the clear surface layer of the eye. It looks alarming but is painless, doesn’t affect your vision, and doesn’t produce any discharge. It can happen from sneezing, coughing, straining, rubbing your eye, or sometimes for no obvious reason at all.
The blood follows gravity, so it often pools in the lower half of the eye. Over 7 to 14 days, the color shifts from bright red to brown and then yellow as your body reabsorbs it. Larger bleeds can take up to three weeks to fully clear. No treatment is needed, and vision stays completely normal throughout.
Dry Eye
When your eyes don’t produce enough tears or your tears evaporate too quickly, the lower portion of the eye dries out first. That’s because the tear film is thinnest near the bottom and gravity pulls moisture downward when you blink. The result is a band of redness across the lower white of the eye, often accompanied by a gritty, sandy, or burning feeling that gets worse as the day goes on or after long stretches of screen time.
Dry eye redness tends to come and go rather than appear suddenly. It’s often worse in air-conditioned rooms, windy weather, or after wearing contact lenses for hours. If this pattern sounds familiar, preservative-free artificial tears are the simplest first step. Blinking more deliberately during screen use also helps, since your blink rate can drop by more than half when you’re focused on a screen.
Allergic Conjunctivitis
Allergies cause redness, itching, and watering that can concentrate in the lower half of the eye. Allergens like pollen, dust, and pet dander settle into the lower pocket of the eyelid (the lower fornix), where they sit in contact with the tissue and trigger inflammation. The key giveaway is itching. If the redness came with an intense urge to rub your eyes, allergies are high on the list.
You’ll often notice both eyes are affected, though one side can be worse. Swelling of the lower eyelid, puffy under-eye skin, and clear, watery discharge are typical. Over-the-counter antihistamine eye drops can relieve symptoms quickly, and rinsing your eyes with artificial tears helps flush out allergen particles.
Eyelid Margin Inflammation (Blepharitis)
Blepharitis is chronic inflammation along the eyelid edges, and when it affects the lower lid, the redness it produces tends to spread onto the nearby white of the eye. You might notice crusty or flaky debris along the base of your lower lashes, especially in the morning. The lower lid can look slightly swollen or feel tender to the touch.
Over time, blepharitis destabilizes the tear film, which creates a cycle: the inflamed lid leads to poor-quality tears, which leads to dryness, which makes the redness worse. Gently cleaning the lower lid margin with a warm, damp cloth once or twice a day is the standard first-line approach. This loosens debris and unclogs the small oil glands that keep your tear film stable.
Episcleritis
Episcleritis causes a localized patch of redness that can appear in any section of the eye, including the bottom half. It involves mild inflammation of the thin tissue layer just beneath the surface of the eye. The redness is more restricted than what you’d see with pink eye, and there’s no discharge or watering. You might feel a mild ache or tenderness, but many people feel nothing at all.
Most episodes clear on their own within one to two weeks. It looks similar to a burst blood vessel, but the color is more of a pinkish-red rather than a solid, blood-red patch. Episcleritis tends to recur in some people, and a small percentage of cases are linked to underlying inflammatory conditions.
Contact Lens Complications
If you wear contact lenses, redness in the lower half of the eye deserves extra attention. The lower portion of the cornea is where contact lens-related peripheral ulcers most commonly develop. These are small (under 2 mm) circular lesions at the edge of the cornea caused by bacterial byproducts trapped under the lens. They typically appear as a single small sore with surrounding redness and can cause mild discomfort or a foreign-body sensation.
After healing, a tiny scar may remain, but because these ulcers form at the periphery of the cornea rather than the center, they don’t interfere with vision. The important step is removing your contacts immediately if you notice new redness with any pain or sensitivity to light, and not reinserting them until the eye has been evaluated.
Signs That Need Prompt Attention
Most causes of lower-eye redness are harmless and self-limiting. But certain symptoms alongside the redness signal something more serious:
- Any change in vision, including blurriness, haziness, or partial vision loss
- Significant eye pain (not just mild irritation or grittiness)
- Sensitivity to light that makes it uncomfortable to be in a normally lit room
- A visible white or gray spot on the colored part of the eye or the clear surface
- Redness that keeps spreading or worsening after several days rather than improving
Sudden vision loss in particular, whether partial or complete, in one eye or both, is a medical emergency regardless of whether pain is present. Redness paired with any of the symptoms above points to conditions like corneal ulcers, acute glaucoma, or internal eye inflammation that need same-day evaluation.