Red eyes can spark a lot of annoying questions from people wondering if you’re sick, upset, or hungover.
But bloodshot eyes can be caused by a bunch of different things. They’re often a sign of another problem—like dry eyes, too little sleep, or even overdoing it on certain eye drops, says Andrew Holzman, M.D., ophthalmologist and regional medical director of TLC Laser Eye Centers in Maryland.
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Here are 10 possible culprits, and how you can fix them.
#1. CAUSE OF RED EYES: YOUR EYES ARE DRY.
When your eyes are dry, they become irritated and inflamed. It’s that inflammation that causes the redness.
Dry eye is more common in adults over 50, but it often affects younger people who spend a lot of time staring at computer screens, says Dr. Holzman.
“We don’t blink as much when we look at screens, which causes dryness,” he says.
Other symptoms: Burning, stinging, and a gritty sort of feeling—like something is in your eye.
How to fix it: Artificial tears can moisten your eyes, which reduces inflammation and eases the redness.
To keep the problem from coming back, try to blink more when you’re at your computer, says Dr. Holzman.
You can also try the 20-20-20 rule to help reset your blinks and reduce the dry-eye issues caused by staring at your computer: Every 20 minutes you’re in front of a screen, focus on something 20 feet away from you for 20 seconds.
If that doesn’t help, you could have chronic dry eye, so see your doctor.
He or she might prescribe eye drops that reduce dryness-related inflammation, like Restasis.
#2: CAUSE OF RED EYES: YOU HAVE SEASONAL ALLERGIES.
Allergens like pollen and grass can cause swelling and inflammation in your eyes, which can lead to redness.
Because allergies also tend to make your eyes itchy, you end up rubbing them, which creates even more inflammation and redness, Dr. Holzman says.
Other symptoms: Itchiness, sneezing, congestion, and watery eyes.
How to fix it: Ease the redness and inflammation by applying cold compresses to your eyes for 15 minutes several times a day, says Dr. Holzman.
Then, talk with your primary care doctor to figure out the best way to keep your allergies under control. He or she might recommend antihistamines, which decrease your body’s response to allergens and ease inflammation.
But because antihistamines make your eyes dry, you might also have to use artificial tears to prevent dryness and redness.
#3: CAUSE OF RED EYES: YOU’RE TAKING CERTAIN MEDS.
Antihistamines aren’t the only medications that can potentially dry out your eyes and leave them red.
Sleeping pills, anti-anxiety meds, and even pain relievers like ibuprofen can also cause dryness and redness.
These medications can reduce blood flow to tissue in and around your eye, making it dry and red, says Jeffrey Anshel, O.D., optometrist and founder of the Ocular Nutrition Society.
How to fix it: Get quick relief from the dryness—and redness—with artificial tears.
But for longer-term relief, talk with the doctor who prescribed your medication. He or she may be able to adjust your dose, or offer an alternative prescription with fewer side effects.
#4: CAUSE OF RED EYES: YOU HAVEN’T BEEN GETTING ENOUGH SLEEP.
Whether you stayed up late watching Netflix or spent half the night tossing and turning, your eyes will probably look a little bloodshot in the morning.
“The eyes need to be closed for an extended period of time for your tear layers to regenerate and replenish. And loss of tears leads to redness,” says Dr. Anshel.
Other symptoms: You might find yourself squinting.
“The eyes’ muscles need to recharge overnight,” Dr. Anshel says.
If they don’t get enough rest, you’ll have a harder time focusing on things both close up and far off.
How to fix it: Again, artificial tears can help you re-moisturize your parched tear layers, Dr. Anshel says. Getting the recommended 7 to 8 hours of sleep can keep the dryness from coming back.
#5. CAUSE OF RED EYES: YOU DRANK TOO MUCH.
It’s not just the fact that you didn’t get home until daybreak.
“Alcohol causes your blood vessels to relax,” Dr. Holzman says. That allows more blood to flow through the vessels in your eyes, so they look redder.
Other symptoms: Headache, dehydration, nausea, and feeling like garbage overall.
Related: 11 Ways to Cure a Nasty Hangover
How to fix it: Use an over-the-counter eye whitening drop, like Visine.
“It works by constricting blood vessels, which reduces blood flow to your eyes so they look less red,” says Dr. Holzman.
It’ll ease the redness within 15 minutes or so. Just don’t go overboard (See #10.)
#6. CAUSE OF RED EYES: YOU’RE A SMOKER, OR HUNG OUT WITH ONE.
Cigarette smoke causes the blood vessels in your eyes to constrict, which dries out the surface of your eyes, Dr. Anshel says.
When your body senses the dryness and lack of blood flow, it tries to compensate by dilating your blood vessels. And that means more redness.
Other symptoms: You might notice dryness in the short term.
In the long-term, the blood vessel constricting-effects of smoking (or exposure to secondhand smoke) can raise your risk for macular degeneration and cataracts—which can cause vision loss and even blindness.
How to fix it: If you smoke, take steps to quit smoking.
If not, seek fresh air. “Your eyes should clear in about an hour,” Dr. Anshel says.
#7. CAUSE OF RED EYES: YOU HAVE PINK EYE.
Pink eye, or conjunctivitis, is a viral or bacterial infection that can strike in one or both eyes.
It’s highly contagious, so it’s easy to spread from one eye to the other by just rubbing your eyes, Dr. Holzman says.
The infection causes inflammation in and around your eye, which makes it look red and swollen.
Other symptoms: Itching or burning, watery eyes, mucus-like discharge, and sensitivity to light.
How to fix it: See your eye doctor, who can examine your eyes to determine whether your pink eye is viral or bacterial.
If it’s viral, you’ll probably have to wait it out, which can take two to three weeks. (Steroid eye drops could help the redness and swelling for really bad viral infections, Dr. Holzman says.)
If it’s bacterial, your doctor will prescribe antibiotic eye drops, which will start soothing your symptoms within a couple of days.
#8. CAUSE OF RED EYES: YOU JUST WENT SWIMMING.
The salt in ocean water is drying, which leads to redness.
And pools contain caustic chemicals, like chlorine, that actually kill off some of the good bacteria in your eyes—which can lead to irritation and redness, Dr. Anshel says.
Other symptoms: Your eyes might also feel dry or irritated.
How to fix it: Flush your eyes with saline solution or artificial tears, which will wash out the irritating gunk and ease the redness, Dr. Anshel says. And if you wore contacts while swimming, take them out and clean them ASAP.
Next time, wear goggles to keep the salt and chemicals out of your eyes.
#9. CAUSE OF RED EYES: YOU POPPED A BLOOD VESSEL.
Popped blood vessels can happen if you were straining (like coughing intensely), if you slept in a weird position that put a lot of pressure on your eye, or experienced some kind of trauma—like getting punched or being in a car accident.
When a blood vessel bursts, blood gets trapped under the surface of your eye.
That can cause a bright red splotch, or make the entire white of your eye turn blood red.
But popped blood vessels aren’t actually serious—they just look bad, Dr. Holzman says.
Other symptoms: Popped blood vessels don’t hurt, but your eye might feel slightly heavy from the extra blood.
How to fix it: Unfortunately, there’s nothing you can do to reduce the redness or speed up the healing.
“It should go away on its own in about a week,” says Dr. Holzman.
#10. CAUSE OF RED EYES: YOU WENT CRAZY WITH THE VISINE
Weirdly, eye whitening drops can actually make your redness problem worse.
That’s because the drops work by constricting the blood vessels in your eyes to reduce blood flow.
“If you use the drops on a regular basis, your body will adapt to the drops,” Dr. Holzman says. “Then when you stop, you end up getting a rebound effect where your blood vessels dilate and your eyes start to look red.”
Other symptoms: They’ll vary, depending on the underlying issue that’s making your eyes red (like drinking, smoking, or allergies).
How to fix it: Using eye whitening drops once in a while (like after a night of drinking) is fine.
But if you’re using them every day for more than a week or two, see your eye doctor to figure out what’s actually causing your redness (often, it’s dryness, Dr. Holzman says).
Once you figure out the root cause, you can treat it.