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what can cause bloodshot eyes

There’s no need to panic if you have bloodshot eyes unless accompanied by extreme discomfort or thick goop draining from the corners or around the eyelashes. However, red or bloodshot eyes always indicate the eyes are unhappy about something.

12 Common Causes For Red Or Irritated Eyes

Here are 12 common reasons eyes may be red, irritated, or bloodshot. 


Any type of allergy can cause red or watery eyes that appear bloodshot. Sometimes it’s the eyes reacting to a direct offender, such as an eye makeup product or hair product that entered the eyes, causing direct inflammation of the tissues. Other times, red eyes are part of the body’s inflammatory response to allergens that enter the sinus or respiratory system. 

Compresses can be used to soothe the eyes, as do over-the-counter allergy eye drops or allergy pills that quell an overactive histamine response.

Common colds and flus

Similarly, eyes are vulnerable to common colds and flus. If you’re not feeling your best and you have red eyes, odds are the bloodshot surfaces are affected by whatever bug or virus you have. If that’s the case, lubricant drops soothe the eyes, and they’ll get better when you do. Take it easy, drink plenty of fluids, and give the contacts a break.

Eye injuries

Sometimes red or bloodshot eyes indicate an eye injury. If your eye was penetrated by something, odds are you were aware when it happened. However, scratched corneas, bits of sand or dust, or even miniscule shards of glass or fiberglass cause severe irritation without patients knowing it happened. If the irritation or discomfort doesn’t resolve with eye flushing, contact your optometrist and check-in. You may need to come in for an exam.

Post-injury healing

If the eye was impaled by something or hit by blunt force during a sporting event, fall, or accident, ruptured capillaries cause mild to severe redness. It’s a good idea to have eye injuries examined by a physician or optometrist to prevent any risk of long-term damage. It can take a few days to a week or so for the broken blood vessels to heal and for redness to fade after treatment.

Contact lens irritation

It can take a while for the eyes to get used to contact lenses. So, many new contact lens wearers may experience a bit of redness or irritation. It’s best to ease into contact lens use as your eyes adjust. However, sometimes long-term wearers develop stop caring for their contacts like they used to or develop contact lens intolerance

Most causes of contact lens irritation are:

  • Poor fit
  • Improper cleaning/storage
  • Wearing them for too long
  • Not being gentle enough when you take them out (which can scratch the surface of the eye)

Try taking a break from contacts and wearing glasses for at least a week or two and see if that helps. If so, don a fresh pair of lenses and honor the care instructions. If irritation continues, schedule an appointment with the optometrist.

Overuse of preservative-laden eye drops

Most over-the-counter eye drops contain additives to increase their shelf life in the market and at home and to force the redness out by depriving the eye of oxygen. One of the chemicals included in those drops is tetrahydrozoline HCL. Its purpose is to constrict blood vessels to decrease redness. If you use them all the time, your eye develops an “addition” of sorts, and the vessels experience “rebound dilation” when you stop using them.

We recommend avoiding eye drops with additives. Eye drops like preservative-free Systane or Refresh are a better bet and don’t have negative side effects.

Too much computer time

The increase of screen time in the average household has led to an increase in cases of eye strain and screen-related eye irritations. Eye doctors refer to this as computer vision syndrome. In addition to bloodshot eyes, those experiencing computer vision syndrome also have symptoms like dry eye or excessive watering. In addition to keeping preservative-free lubricant drops near your computer, take regular breaks away from the screen – preferably every 20 minutes or so.

Any number of eye infections or inflammation

Any type of infection affecting the surface or interior of the eye causes irritation and often presents via bloodshot eyes. Things like styes or inflamed eyelids can also cause red eyes. Eye infections typically resolve on their own but are highly contagious, so we always recommend assessing them via a video call or appointment with a physician or optometrist.

Lack of sleep

What’s your sleep schedule like? If you’re like most of our patients, you don’t get enough. Establishing a healthy sleep cycle is essential for overall well-being and helps reduce eye strain and irritation.

Drug and alcohol use is a common cause of bloodshot eyes

Some drugs are known for causing bloodshot eyes, such as marijuana (cannabis) and cocaine. Consuming alcohol, especially in excess, also causes bloodshot and glassy eyes. In fact, bloodshot eyes are one of the things police officers look for at routine road checkpoints. First and second-hand cigarette smoke is also an eye irritant.

Overexposure to UV rays

Anyone who spends ample time outside without proper eye protection can experience photokeratitis. Surfers, skiers/snowboarders, swimmers, etc., are at especially high risk as they spend large amounts of time on the water or in the snow, which magnifies the sun’s UV rays. Always wear UV-blocking sunglasses outdoors during daytime hours – even if it’s a cloudy day. 

In addition to bloodshot or red eyes, symptoms of photokeratitis include:

  • Watery eyes
  • Itchy or gritty feeling
  • Sunburns on other parts of the body
  • Light sensitivity
  • Eye drainage
  • Blurred vision or difficulty seeing

Repeated episodes of photokeratitis lead to long-term eye and vision damage.

Dry eye

Patients with dry eyes often experience the sensation of dry or scratchy eyes. In addition, the eyes are frequently red or irritated and may tear excessively. Eye drops may soothe the symptoms and help them resolve on their own. Practicing good screen boundaries (taking lots of breaks), staying hydrated, and getting plenty of sleep also help. In chronic cases, we prescribe special drops or ointments.

Let AEI Treat Your Bloodshot Eyes

Do you suffer from chronically bloodshot eyes? Or, do you have bloodshot eyes accompanied by pain or discomfort? Schedule a video exam with the Atlantic Eye Institute, and we’ll take it from there. 

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