8 Reasons Why Your Eyes Are Red—and How To Treat Them

If the eyes are the windows to the soul, bloodshot eyes are the windows to your health.

If you see red eyes looking back at you in the mirror, they could be letting you know something's happening with your eyes or another part of your body. But because so many conditions can cause one or both of your eyes to be red, it's not always easy to figure out what's causing the redness—and what you can do about it.

"Usually, the eyes turn red because the blood vessels on the surface of the eye get dilated or inflamed," explained Jessica Lee, MD, assistant professor of vitreoretinal surgery, department of ophthalmology at the New York Eye and Ear Infirmary of Mount Sinai. "And there is a multitude of reasons that can happen."

Some of those reasons are simple and have an easy fix, while others are more serious. Red, inflamed, or itchy eyes could be the first sign of a condition that may impact your vision. 

Here's what you should know about what causes red eyes to better determine why your eyes may look bloodshot and how to treat them.

Allergies

An allergic reaction can make your eyes feel bad—think itchy, tender, and watery. But it can also trigger a blotchy redness, which only worsens if you scratch your eyes, according to the National Library of Medicine.

"Allergic reactions occur when the body's natural immune system overworks or has an excessive response to a harmless stimulus," said Dr. Lee. 

Almost anything can set off a reaction, but the most common allergens are dust, pollen, pet dander, and detergent. 

Try to figure out what caused your reaction and avoid coming into contact with it again, advised Dr. Lee. The redness will start to go away once you are no longer exposed to the allergen, but that can take a while, depending on the severity of your allergy. 

In the meantime, splash your eyes with water, or use a cool compress to speed things up. Over-the-counter (OTC) eyedrops designed to combat allergies can help, as can antihistamine medications.

Pink Eye

"Pink eye is the non-medical term for conjunctivitis—a bacterial, viral, or allergy-induced infection that leaves one or both eyes bright red, swollen, teary, and itchy," explained Dr. Lee. 

Though it rarely becomes serious, pink eye spreads quickly. It can turn your eyes goopy and pinkish-red and keep you away from work for several days, per the Johns Hopkins Medicine Health Library.

Pink eye doesn't require a visit to a healthcare provider. A cold compress can help ease the redness and make your eyes feel better. But if you're unsure whether you have pink eye or if the infection doesn't go away in a few days, check in with your healthcare provider. 

Your pink eye type will determine how and if your healthcare provider can treat it. For example, if it's a bacterial infection, antibiotic eyedrops can help.

If you have viral or bacterial conjunctivitis, practice good hand hygiene to keep it from spreading to other people in your household. Sharing towels or makeup, touching your eyes, and then making contact with another person can transmit pink eye.

Heavy Alcohol Use

After you drink a lot of alcohol, you may notice that your eyes sport bright red spider veins on them. That's alcohol's effect on the eyes. 

Alcohol causes the tiny blood vessels in the eyes to dilate—so more blood flows through them. 

"The more you drink, the more visible and red they appear against the whites of your eyes," explained Dr. Lee.

OTC eye drops can reduce redness. And as the alcohol leaves your system over a few hours, the blood vessels will return to normal.

Too Little Sleep

Tired eyes tend to be bloodshot eyes. That's because a lack of sleep can decrease the amount of oxygen that reaches your eyes, which in turn causes blood vessels on them to dilate and appear red.

 "If your eyes are kept open for a long time because of lack of sleep, it prevents the cornea [the surface of your eye] from being well lubricated, and this can cause dryness and redness," explained Dr. Lee. "The best way to calm them would be to get more sleep and use artificial tears and cool compresses to ease the discomfort."

In one study published in 2022 in the journal Cureus, researchers reported that there was a positive correlation between people with sleep deprivation and dry eyes.

A Stye

According to the National Library of Medicine, a stye is a small red bump that forms on your eyelid (or the bottom edge of your eye) after an oil gland becomes plugged up.

You could have one or several, and each will resemble a pimple or boil. One of the first signs is redness, along with swelling and sensitivity. Styes are caused by bacteria, and almost everyone will have them at some point.

Luckily, a stye doesn't affect your vision. But it can still be bothersome, and getting rid of it generally involves waiting and letting it go away on its own in several days. 

Touching the stye can worsen it, so avoid popping it. That can also exacerbate the infection. If you get styes frequently, see an ophthalmologist, who may prescribe an antibiotic ointment.

Contact Lens Irritation

"Contact lenses can prevent enough oxygen from reaching your eyes, leaving you with bloodshot and irritated eyes," explained Dr. Lee. "If the lenses are worn too long or worn while sleeping, they can cause redness, infections, and in worst-case situations, corneal ulcers."

Steer clear of those issues by closely following the lens care directions, cleansing them properly, practicing good contact lens hygiene, and taking the contacts out before falling asleep, per an article published in 2017 in the Morbidity and Mortality Weekly Report.

In the meantime, eye drops can ease the redness and soothe irritation.

A Subconjunctival Hemorrhage

According to the National Library of Medicine, a subconjunctival hemorrhage happens when a blood vessel under the eye surface breaks. When that happens, blood gets trapped and forms a bright red patch in the white of the eye. 

It's a common injury, and though the hemorrhage looks serious, it won't likely affect vision or cause pain, discharge, or swelling. The red patch usually fades over a few weeks.

A subconjunctival hemorrhage can be brought on when you overexert yourself at the gym, lifting something heavy, or even a strong sneeze or cough. Throwing up can trigger hemorrhaging, as it can direct trauma to your eye.

Glaucoma

Glaucoma damages the optic nerve, which connects the eye's retina to the brain, when too much pressure is put on the eye. That's typically due to fluid buildup, per the Johns Hopkins Medicine Health Library.

One of the first signs of one type of glaucoma—called angle-closure glaucoma—is redness. Other signs include cloudy vision, seeing halos around lights, swollen eyes, pain in the eye, and nausea and vomiting.

Glaucoma can cause blindness, so you must see an eye specialist for a complete exam if you suspect you may have it. 

Typically, glaucoma progresses slowly, but if the redness and vision problems pop up suddenly and you also experience headaches or nausea, it may be a medical emergency.

Glaucoma is more common among older adults but can develop at any age. Getting regular eye exams can catch it early and slow down vision loss with the help of medication.

Red, bloodshot eyes can be caused by many conditions. And several of those are usually cleared up by a quick course of antibiotics or even a few eye drops.

But if you experience symptoms of a more serious condition, like glaucoma, it's important to see a healthcare provider as soon as possible. Symptoms like severe eye pain, frequent and painful headaches, blurred vision, and halos around lights are among some of the most common symptoms of glaucoma, which can lead to permanent blindness.