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A person can have red eyes for many reasons. For example, red eyes can indicate minor irritation or a more serious condition, such as an infection.

Red or bloodshot eyes occur when small blood vessels on the surface of the eye become enlarged and congested with blood.

Red eyes alone are not usually a reason for concern. However, if there is also eye pain, watering, dryness, or impaired vision, this can indicate a serious medical problem.

This article looks at some possible causes of red eyes in more detail. It also covers some treatment options.

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Conjunctivitis, or pink eye, is an infection that includes swelling and irritation of the conjunctiva. The conjunctiva is a thin transparent membrane that lines the inside of the eyelid and loops back to cover the white part of the eye.

An infection of the conjunctiva irritates the blood vessels, causing them to swell. This inflammation makes the whites of the eyes appear reddish or pink.

Viruses cause up to 80% of all conjunctivitis cases. Other causes include bacteria, fungi, exposure to chemicals or allergens, a foreign body in the eye, and the use of contact lenses.

The infection commonly spreads through direct contact with contaminated fingers or personal items. It can be associated with an upper respiratory infection, and people can pass it on through coughing.

Pink eye often affects both eyes because the infection typically spreads from one eye to the other.

Some signs and symptoms of conjunctivitis include:

  • itchy eye
  • excess tear production
  • redness
  • discharge
  • sensitivity to light
  • poor vision
  • a gritty feeling in one or both eyes

A doctor will usually diagnose pink eye by looking at the symptoms and assessing the type of discharge present. With bacterial conjunctivitis, the discharge is often white, green, or yellow, and it can seem like pus. The doctor may also take a sample of the discharge for laboratory analysis.

Treatment options depend on the cause of the conjunctivitis. The doctor will recommend a suitable option. Viral conjunctivitis can go away without treatment and does not typically cause any long-term problems.

To avoid spreading conjunctivitis, people should:

  • Wash the hands frequently.
  • Avoid rubbing the eyes.
  • Avoid sharing eye drops, cosmetics, towels, or pillowcases.
  • Remove contact lenses at night.

After conjunctivitis clears up, a person should dispose of any contact lenses, solutions, or eye makeup they used during the infection to help prevent reinfection.

Get some tips on treating pink eye at home here.

Allergic conjunctivitis can develop due to an allergy or an irritant, such as dust, pollen, or animal dander. Contact lenses and lens solution may also trigger a reaction. In addition, if a person wears contact lenses for too long, conjunctivitis can arise due to irritation.

Conjunctivitis due to allergies or irritants is not contagious.

If a doctor suspects an allergy, they may carry out an allergy test to determine the trigger. However, the most common cause is a seasonal allergen, such as pollen.

A person who knows that they have an allergy or sensitivity reaction to pollen or other allergens should take care to avoid exposure, where possible.

A corneal ulcer is an open sore on the cornea that can result from a bacterial, viral, fungal, or parasitic infection. Scratches, burns, dry eye syndrome, and conditions that affect eyelid function can also increase the risk.

Contact lenses can rub against the eye’s surface and slightly damage the outer cells. This damage may allow pathogens to penetrate the eye.

Symptoms can include:

  • red eyes
  • pain or soreness
  • sensitivity to light
  • mild-to-severe eye discharge
  • reduced vision
  • a white spot on the cornea

Without appropriate treatment, corneal ulcers can lead to vision loss, so this is a medical emergency. Treatment options include antibiotics and antifungal agents. Serious cases may require a cornea transplant.

A person whose body does not produce adequate tears to lubricate and nourish the eyes may develop dry eye syndrome.

Hormonal changes, some medical conditions, and some medications can cause dry eye syndrome. Chronic dry eye can cause the surface of the eye to become red, inflamed, and irritated.

Some people experience dry eyes with COVID-19.

Symptoms of dry eye syndrome include:

  • stinging or burning eyes
  • a feeling that something is in the eye
  • pain and redness in the eye
  • excessive tears
  • discomfort when wearing contact lenses
  • blurry vision
  • eye fatigue
  • stringy eye discharge
  • discomfort after watching television or reading

A doctor can determine if dry eyes are due to an underlying medical condition. An ophthalmologist can perform tests to measure tear production, if necessary.

For mild cases, over-the-counter medications — such as artificial tears, gels, or ointments — may be helpful. Other options include prescription eye drops and surgery, depending on the severity of the condition.

Some lifestyle tips for preventing dry eye syndrome include:

  • limiting screen time
  • avoiding smoke, wind, and air conditioning, where possible
  • wearing wraparound sunglasses
  • getting enough sleep
  • drinking plenty of water

Get some more tips on treating dry eye syndrome here.

The conjunctiva contains many blood vessels and capillaries. If these vessels break, blood can leak into the area between the conjunctiva and the white of the eye.

When this happens, a small amount of blood builds up under the conjunctiva. This small accumulation of blood is called a subconjunctival hemorrhage. The minor bleeding under the eye’s outer membrane causes bright red spots to appear on the white on the eye.

A subconjunctival hemorrhage can result from a minor injury or trauma to the eye, including rubbing the eye due to allergies.

Common causes also include coughing, sneezing, and straining. People who have diabetes, have high blood pressure, or take certain medications, such as blood thinners, may have a higher risk.

Subconjunctival hemorrhages occur on the surface of the eye. Because they do not affect the cornea or the interior of the eye, they do not impact vision.

They are not usually painful, and the only symptoms may be red spots in the white of the eye. Although redness or blood in the eye can look serious, most subconjunctival hemorrhages are generally harmless and will clear up on their own within a few days.

Usually, no treatment is typically necessary. If irritation occurs, however, a doctor may recommend artificial tears.

What else can cause bleeding in the eyes? Learn more here.

Various medical conditions can cause red eyes, such as:

If red eyes occur with other symptoms, a person should contact a doctor.

Red eyes often get better without treatment, but eye drops may help ease any discomfort.

However, a person should seek medical help if they have:

  • an eye injury
  • persistent symptoms
  • pain
  • vision loss

Common treatments include eye drops, antibiotics, creams, and oral medications. Most cases of red eyes are very treatable and, if caught early, do not cause any permanent long-term damage.

If red eyes result from an underlying condition, a doctor will need to treat this condition.

Which eye drops are good for people with red eyes? Find out here.

The eyes can become red for many reasons. Often, the redness goes away without treatment. Sometimes, however, red eyes can be a symptom or a more serious condition. Some causes of red eyes can even lead to vision loss.

Anyone who has concerns about red eyes should seek medical help.

Various types of eye drops are available for purchase online here.

Read the article in Spanish.