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Why Are My Eyes Red?

Dr. Jordan Marr

Written By:

Dr. Jordan Marr

Updated: 30 September 2022 •  

Red eyes are something that most of us have experienced at some point. Bloodshot eyes can be caused by a wide range of factors that have different symptoms and treatments. While most cases are harmless and go away on their own, it is important to know how you can manage red eyes and when you should seek medical attention.
 

What are red eyes?

A red eye is when the eye looks red, irritated, or bloodshot. This is caused by dilation or swelling of the small blood vessels in the eye. Usually, a red eye is painless and does not affect vision or cause discomfort.
 
Sometimes, red eyes can cause pain, photophobia (light sensitivity), and blurred vision. If you experience any of these three symptoms, you should seek medical advice.
 

The most common causes of red or bloodshot eyes

Determining the cause of bloodshot eyes is not always straightforward, as there are many different factors to consider. Red eyes can be as simple as not getting enough sleep, or irritation from chlorine swimming pools. They can also be caused by underlying conditions or infection.
 
Some of the common causes of red eyes include:
 

  • Dry eyes (or Dry Eye Syndrome)This often happens when you do not produce enough tears to keep the front of your eye moist, or if you do not produce enough oil to prevent your tears from evaporating. Dry eye can occur from staring at screens, lack of sleep, medications, or exposure to dry weather or wind.
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  • AllergiesWhen exposed to allergens (such as pollen or dust), the body produces histamines which can cause inflammation. This makes the eye red, watery, and itchy.
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  • Contact lensesWearing contact lenses prevents oxygen in the air from reaching the front of your eye which causes the blood vessels to expand. It is important to only wear contact lenses for the recommended time, and not to sleep or swim while wearing contact lenses to avoid this.
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  • Conjunctivitis (or pink eye)Pink eye is inflammation of the conjunctiva, which is the clear, protective layer that covers the front of the eye and inside of the eyelid. This can be caused by allergies, bacteria, viruses, fungus, or chemicals. Conjunctivitis can also cause discharge from the eye that may be watery or sticky and mucopurulent (yellow/white pus).
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  • Subconjunctival haemorrhageThis happens when a blood vessel under the conjunctiva bursts and looks as though the eye is “bleeding”. Since the blood is trapped under the front layer of the eye, it has nowhere to go and thus spreads. Common causes of subconjunctival haemorrhage include sneezing or coughing too hard and lifting heavy objects. While this may look scary, it usually goes away on its own and is nothing to worry about.
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  • EpiscleritisThis is an inflammation of the layer covering the sclera (the white part of your eye) which is underneath the conjunctiva. This can cause some mild pain and irritation but does not affect vision. Episcleritis can be spontaneous (appears on its own with no obvious cause) or can be triggered by immune conditions such as rheumatoid arthritis or lupus. Episcleritis usually goes away on its own. If you experience episcleritis repeatedly, you should see your doctor for a check-up.

 

Other, rarer causes of red eyes

Some of the more uncommon causes of red eyes include:
 

  • ScleritisUnlike episcleritis, scleritis is much more serious and can cause extreme light sensitivity and blurred vision. The eye and face might be sore, and there is a potential for complete vision loss. Scleritis requires treatment with corticosteroids (reduces inflammation) and antibiotics. In severe cases, you may require surgery.
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  • UveitisUveitis is inflammation inside of your eye and can involve the front (anterior uveitis), middle (intermediate uveitis), back (posterior uveitis), or all (panuveitis) of your eye. Uveitis causes a dull, aching pain, light sensitivity, and blurry vision. You may also see floaters (dark squiggly lines or spots) in your vision. Uveitis can be treated with steroids.
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  • Acute angle closure glaucomaA sudden increase in intraocular (eye) pressure can block the eye’s drainage channel and cause dilated blood vessels, leading to red eyes. Your cornea (the clear part of the eye covering your iris and pupil) may become hazy and your pupils will not constrict when exposed to direct light. This requires urgent treatment to avoid permanent vision loss, which includes medications to reduce eye pressure and potential surgery to increase drainage in your eye.
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  • Smoking or alcoholSmoking can expose the eye to harmful chemicals that cause inflammation of the eye’s blood vessels. Alcohol can cause the blood vessels in the eye to dilate, making them appear bloodshot.

 

How to treat common causes of red eyes

Many types of red eyes can be avoided by taking extra care. Some ways of preventing red eyes include:
 

  • Regularly wash your eyelidsGently washing your eyelids and surrounding facial skin with clean warm water removes debris and bacteria that may cause irritation or infection. It is also important to remove your eye makeup properly to prevent irritation.
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  • Keep your eyes hydratedYou can do this by drinking enough water and using lubricating eye drops.
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  • Reduce your screen timeSpending less time on screens, or taking more frequent breaks, will prevent your eyes from becoming dry and fatigued.
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  • Get enough sleepThis allows your eyes time to recover and rehydrate.
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  • Avoid allergens and irritantsIf you are aware of certain allergies, such as dust or animal fur, then you should try to avoid exposure to them. It is also a good idea to keep your environment clean by regularly removing dust from your surroundings (by sweeping, vacuuming) and washing your bed linen.
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  • Try not to rub your eyesRubbing your eyes can introduce bacteria and debris, which can cause irritation or infection.

 
If you have a red eye, the remedy will depend on the cause. Some common ways of managing a red eye include:
 

  • Artificial tear eye dropsThese will rehydrate dry eyes and flush out allergens and irritants.
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  • CompressesCool compresses are best for red eyes caused by irritation or inflammation as they relieve the eyes and reduce swelling. Warm compresses are best for dry eyes and bacterial causes of red eye, as they loosen blocked oil glands and dried mucus.
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  • AntihistaminesIf your allergies have caused your eyes to become red, then antihistamines will prevent your body from producing the histamines that cause inflammation and irritation to your eyes and sinuses.

 
In other types of red eyes, you may be prescribed antibiotic drops or steroid drops to treat the cause of your red eye and to reduce inflammation.
 

Should I use eye-whitening eye drops for my red eyes?

Eye whitening eye drops, also known as redness relieving drops, are often used to reduce the red appearance in bloodshot eyes. These drops work by causing the eye’s blood vessels to constrict (vasoconstriction). A common brand of these drops is Visine.
 
While it may be tempting to use these drops to improve the appearance of your red eyes, it is important to understand that these drops often have a “rebound” effect, especially if used for long periods of time. When you stop using these drops, your eye’s blood vessels will become even more dilated than they were before, causing your eyes to look redder.
 
As well as making the eyes even redder than they were initially, these drops do not treat the cause of your red eyes. This means that your bloodshot eye may keep coming back if you do not manage its cause.
 

When to call the doctor about red eyes

Although most causes of red eyes are harmless, sometimes they can be something more. If you are experiencing symptoms such as headaches, nausea or vomiting, fevers, discharge from the eyes, or swelling around the eyes then you should seek medical attention. If your red eyes are not going away on their own or are getting worse, then you should also see a health professional.
 
The three main “red flag” symptoms that may suggest the need for medical treatment are:
 

  • Reduced vision
  • Photophobia (light sensitivity)
  • Pain

 
If in doubt, it is best to see an optometrist or ophthalmologist about your red eyes – especially if you are unsure of its cause. This will ensure that the cause of your red eye is nothing sinister, and your health professional will provide you with the most accurate advice to resolve the red eye more quickly.
 

References

  • “Red Eye”, Mayo Clinic
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  • “Red Eye – A Guide for Non-Specialists”, Deutsches Arzteblatt International Journal
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  • “Uveitis”, National Eye Institute
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  • “Home Remedies for Bloodshot Eyes”, American Academy of Ophthalmology
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  • “Redness-Relieving Eye Drops”, American Academy of Ophthalmology
Dr. Jordan Marr

Written by:

Dr. Jordan Marr

Dr Jordan Marr has over 5 years of clinical and academic optometry experience and is a visual science editor for the Clinical and Refractive Optometry journal. He is licensed under the Optometry Board of Australia.
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