Red eyes happen when the tiny blood vessels on the surface of your eye become swollen or irritated, making the white part look pink or bloodshot. Most of the time, the cause is something mild and temporary like allergies, dryness, or a late night. But the specific pattern of redness, along with any other symptoms you notice, can tell you a lot about what’s going on.
The Most Common Causes
A few culprits account for the vast majority of red eyes. Allergies are one of the most frequent, and the giveaway is intense itching along with watery, teary eyes. Dry eye is another major one, especially if you spend long hours looking at screens or live in a dry, windy climate. When your tear film breaks down or evaporates too quickly, the surface of your eye becomes irritated. That irritation triggers a cycle of inflammation that makes the redness persist and often worsen over time.
Lack of sleep, drinking alcohol, smoke exposure, and general eye strain can also leave your eyes looking bloodshot. These causes tend to resolve on their own once the trigger is removed.
Pink Eye and How to Tell Which Type You Have
Conjunctivitis, or pink eye, is one of the first things people worry about when their eyes turn red. There are three main types, and they look and feel quite different from each other.
Viral conjunctivitis produces a clear, watery discharge and often a gritty sensation, as if something is stuck in your eye. It’s highly contagious and spreads through direct contact or contaminated surfaces. It typically starts in one eye and moves to the other within a day or two.
Bacterial conjunctivitis is the one that produces thick, yellow or greenish discharge. You may wake up with your eyelids stuck together. It’s also highly contagious and can spread through direct contact or poor hygiene.
Allergic conjunctivitis stands out because the itching is intense, often the dominant symptom. The discharge is mostly just excess tearing. The key difference: it’s not contagious at all. It’s your immune system reacting to pollen, pet dander, or dust mites, and it almost always affects both eyes at once.
A Bright Red Patch on the White of Your Eye
If instead of general pinkness you see a vivid, solid red spot on the white of your eye, that’s likely a subconjunctival hemorrhage, which is a broken blood vessel. It looks alarming but is usually painless and harmless. Common triggers include rubbing your eye too hard, sneezing or coughing forcefully, straining while lifting something heavy, or even just bending forward. Contact lens wear, blood thinners, high blood pressure, and diabetes can also increase your risk.
These red spots typically clear on their own within about two weeks. The blood slowly gets reabsorbed, and the spot may shift color from red to yellow before disappearing completely. No treatment is needed in most cases.
Contact Lenses and Red Eyes
Contact lens wear is one of the most common reasons otherwise healthy eyes become red. Lenses sit directly on the cornea, reducing oxygen flow and creating conditions where bacteria can thrive. The CDC links contact lens use to a higher risk of corneal inflammation, which in severe cases can lead to permanent vision damage or the need for a corneal transplant.
Less serious but still bothersome complications include dry eyes, allergic reactions, corneal scratches, and a condition called giant papillary conjunctivitis, where bumps form underneath the eyelid. Some long-term wearers develop new blood vessels growing onto the cornea, a sign the eye is starved for oxygen. If your eyes are consistently red and you wear contacts, switching to glasses for a few days often reveals whether the lenses are the problem.
Why “Get the Red Out” Drops Can Backfire
Over-the-counter redness-relief drops are tempting, but they come with a catch. Most contain a decongestant called tetrahydrozoline that works by squeezing the blood vessels on your eye’s surface. The redness disappears temporarily, but when the drops wear off, those vessels can dilate even more than before. This rebound redness often worsens with repeated use, creating a cycle where your eyes look worse without the drops than they did before you started using them.
A newer type of redness-relieving drop uses a different active ingredient (brimonidine) that carries a lower risk of rebound redness but still works by constricting blood vessels. For most cases of mild redness, artificial tears or lubricating drops are a safer choice because they address the underlying dryness or irritation instead of just masking the symptom.
What Helps at Home
For garden-variety redness from allergies, dryness, or irritation, a cool compress placed over your closed eyes for a few minutes, a couple of times a day, can reduce swelling and soothe discomfort. Preservative-free artificial tears help restore moisture without the rebound risk of decongestant drops. If allergies are the trigger, over-the-counter antihistamine eye drops target the itch and redness at the source.
Taking breaks from screens using the 20-20-20 rule (every 20 minutes, look at something 20 feet away for 20 seconds) helps reduce the strain that contributes to dryness and redness. If you wear contacts, make sure you’re replacing them on schedule and never sleeping in lenses that aren’t designed for overnight wear.
When Red Eyes Signal Something Serious
Most red eyes are not emergencies. But certain combinations of symptoms point to conditions that can threaten your vision if not treated quickly.
Acute angle-closure glaucoma is one of the most dangerous causes of a red eye. It happens when fluid pressure inside the eye spikes suddenly. The symptoms are hard to miss: severe eye pain, headache, nausea or vomiting, blurred vision, and seeing rainbow-colored halos around lights. This is a medical emergency that requires immediate treatment to prevent permanent vision loss.
Inflammation deeper inside the eye, affecting the colored iris or the middle tissue layer, can also cause redness alongside pain and light sensitivity. These conditions sometimes occur on their own but can also be linked to autoimmune diseases throughout the body. Infections of the tissue around the eye socket are another serious possibility, typically causing significant swelling alongside redness.
Seek immediate care if your vision changes suddenly, you have severe eye pain combined with a headache or fever, light becomes painful to look at, you feel nauseous or are vomiting, you see halos around lights, you have significant swelling around the eye, or you got a chemical splash or foreign object in your eye. Any of these alongside redness suggests something beyond a simple irritation that needs prompt evaluation.