Now let’s explore the different causes of eye redness. For each one, we’ll cover what it is, what causes it, and any other additional symptoms to be aware of.
Allergies
Allergies can affect the eyes, leading them to become red and swollen. Other symptoms that you may experience include:
Eye allergy symptoms can also be accompanied by other allergy symptoms, such as sneezing and an itchy, running nose.
Some common allergy triggers include:
Dry eyes
Tears are made by small glands above the eyes. They work to help protect and lubricate the eyes. You have dry eyes when your eyes don’t produce enough tears.
Dry eyes are very common, with studies estimating a prevalence rate of between 5 to 50 percent. The condition is more likely to occur in women, people over the age of 50, and individuals who wear contact lenses.
If you have dry eyes, you may notice that your eyes appear red. Other symptoms include:
Conjunctivitis
Conjunctivitis happens when the membrane covering the insides of your eyelids and the white part of your eye, called the conjunctiva, becomes inflamed. This condition is also called pink eye.
Inflammation of the conjunctiva causes the whites of your eyes to appear pink or red in color. Some other symptoms that may occur with conjunctivitis are:
- itching
- a burning sensation
- feeling like something is in your eye
- increased tearing
- discharge of mucus or pus, which can lead to crusting of the eyelids or eyelashes
Conjunctivitis can have a variety of causes, including:
- viral infections, such as those due to adenoviruses, measles, or COVID-19
- bacterial infections that can be caused by species like Staphylococcus aureus, Streptococcus pneumoniae, or Haemophilus influenzae
- allergies to things like pollen, molds, and pet dander
- environmental irritants like smoke or chemical fumes
Conjunctivitis due to a viral or bacterial infection is very contagious. That means that it can easily be spread from one person to another.
Blepharitis
Blepharitis is when your eyelids become inflamed. It can cause your eyelids or eyes to appear red and swollen.
Some additional symptoms of blepharitis are:
- itching
- a burning or stinging sensation
- feeling like something is in your eye
- increased tearing
- crusty eyelids in the morning
- sensitivity to light
It’s also possible for blepharitis to cause more serious symptoms, particularly if not managed. These can include things like loss of eyelashes, eyelashes that grow in the wrong location, or blurred vision.
Blepharitis can happen if you have high amounts of bacteria on your eyelids. The condition may also develop if oil glands in your eyelids become clogged. A mite infestation can also cause blepharitis in rare cases.
Uveitis
Uveitis is inflammation that happens in the middle part of your eye, called the uvea. The uvea is an area found between the white of your eye and your retina.
Inflammation due to uveitis can lead to eye redness. Additional symptoms to look out for are:
There are a few known causes of uveitis, including:
Getting timely treatment for uveitis is vital. This is because the condition can lead to vision loss if not managed.
Scleritis
Scleritis is when inflammation affects the white of your eye, which is called the sclera. When this occurs, the white of your eye can become red and swollen. Additional symptoms can be:
- increased tearing
- eye tenderness or pain
- blurred vision
- sensitivity to light
- pain in the head, face, or jaw
- decreased vision
The development of scleritis is often associated with an autoimmune disease. Examples include:
It’s also possible for scleritis to happen due to an injury to the eye or an eye infection.
Subconjunctival hemorrhage
Sometimes, a blood vessel in an eye can break, leaking blood on the surface of your eye This is called a subconjunctival hemorrhage.
The condition may look serious, but it’s often benign and goes away on its own in
However, if you have subconjunctival hemorrhage and your vision is decreased, talk with a doctor.
Some potential causes of subconjunctival hemorrhage are:
- rubbing your eyes too hard
- intense coughing or sneezing
- vomiting
- eye injury
You may be more prone to this condition if you’re taking blood thinners or have diabetes or hypertension.
Eyelid stye
A stye is a blockage of the meibomian gland in the eye that causes inflammation. It can affect the outside or inside of either your upper or lower eyelid.
If you have a stye, the area at the edge of your eyelid can become red, swollen, and painful. The affected area may fill with meibum (due to the blocked gland) and can potentially grow to the size of a pea.
Angle-closure glaucoma
Glaucoma is a condition where the pressure in your eye increases due to the eye producing more fluid than the normal rate. This can damage your optic nerve, potentially leading to vision loss.
There are different types of glaucoma. In one type, called angle-closure glaucoma, a rapid increase in eye pressure occurs. You may also see this type of glaucoma called closed-angle glaucoma or narrow-angle glaucoma.
The symptoms of angle-closure glaucoma come on suddenly and may include eye redness. Other symptoms to be aware of are:
Angle-closure glaucoma happens when your iris blocks the area through which eye fluid drains. Fluid begins building up in the eye, leading to a rapid increase in eye pressure. This type of glaucoma is an emergency and can lead to vision loss if you don’t seek treatment right away.
Corneal ulcers
Corneal ulcers are ulcers, or sores, that affect the outer part of your eye, which is called the cornea. This condition is also called keratitis.
In addition to red eyes, other symptoms of a corneal ulcer are:
- severe eye pain
- feeling like something is in your eye
- increased tearing
- discharge of pus
- blurred vision
- sensitivity to light
- eyelid swelling
There are several things that can cause corneal ulcers to develop:
- bacteria
- viruses, particularly herpes simplex virus and varicella-zoster virus
- fungi
- acanthamoeba, a type of parasitic infection
- dry eyes
- sleeping in contact lenses
- showering or swimming in contact lenses, or using well water to clean contacts
- injury to the cornea, such as a scratch, cut, or burn
- Bell’s palsy and other disorders affecting the eyelid’s ability to close
It’s important to seek timely medical attention if you have symptoms of a corneal ulcer. If not managed, this condition can permanently damage your vision.
Injury
Sustaining an injury that affects your eye may cause it to become red, often due to irritation or bleeding. Other symptoms that may occur with an eye injury are:
- eye pain
- swelling of the eye or the surrounding area
- trouble moving your eye
- decreased vision
- different pupil sizes
A few examples of common sources of eye injuries include:
- foreign objects that get into your eye
- physical trauma, such as sustaining a blow or an accident
- exposure to chemicals
Contact lens wear
Individuals who wear contact lenses have to touch their eyes and the surrounding area more often than those who don’t wear contact lenses. As such, they’re at an increased risk of eye redness due to a variety of factors. Some of these include:
- scratches or scrapes on the cornea
- eye allergies
- eye infections
- corneal ulcers, which can happen from sleeping in contact lenses
- dry eyes
- neovascularization, when new blood vessel grow on the cornea
- giant papillary conjunctivitis, a type of conjunctivitis in which bumps develop under your eyelid
- contact lens-induced acute red eye (CLARE), an inflammatory condition associated with wearing contacts overnight
In addition to eye redness, some symptoms of complications related to contact lenses are:
- eye pain
- increased tearing
- blurry vision
- sensitivity to light
If you wear contact lenses and have any of the symptoms above, remove your contacts for a few hours. If your symptoms continue or become worse, contact an eye doctor.
Additional causes of eye redness
In addition to the causes discussed above, some further causes of eye redness include:
- use of alcohol or cannabis
- photokeratitis, which is eye irritation that can happen due to sun exposure
- ocular rosacea, a skin condition that most often affects the cheeks, nose, or forehead but can also affect your eyes
- trichiasis, in which eyelashes grow inward and irritate the eye
- cellulitis, a bacterial skin infection that can affect the eyelid or eye socket
- endophthalmitis, an infection of the tissues on the inside of your eye
- onchocerciasis, a parasitic infection caused by a roundworm
- retinoblastoma, a type of cancer that affects the eye
