Why Are My Eyes Red?
The honest verdict
This is frequently allergy-related
Red eyes are often caused by allergies — specifically allergic conjunctivitis, which occurs when the eyes react to airborne allergens like pollen, dust mites, pet dander, or mold. Allergic red eyes are typically itchy, watery, and affect both eyes at once. However, red eyes can also result from dry eye syndrome, infections (viral or bacterial conjunctivitis), irritants (smoke, chlorine, contact lens overwear), or more serious conditions like a corneal abrasion, uveitis, or acute glaucoma. The presence of itching strongly suggests an allergic cause, while pain, light sensitivity, or vision changes point to something more serious.
This is a general research summary, not a diagnosis. It can't tell you what's causing your symptom — a clinician can.
Check this first
When red eyes is an emergency
Most of the time this can be handled calmly. But a few signs mean you shouldn't wait. Match what you're seeing to the right level of care below.
If any emergency sign below is present, call 911 or go to the ER now.
- Emergency
Red eye with severe pain, especially with nausea or vomiting — call 911 (possible acute angle-closure glaucoma, a medical emergency).
Call 911 or go to the ER now
- Emergency
Sudden vision loss, blurred vision, or seeing halos around lights — go to the ER (possible glaucoma, retinal detachment, or optic neuritis).
Call 911 or go to the ER now
- Emergency
Red eye with a visible foreign body (e.g., metal, glass) or after a chemical splash — flush with water for 15 minutes and go to the ER.
Call 911 or go to the ER now
- Urgent
Red eye with severe light sensitivity (photophobia), pain, or a change in pupil shape — see an eye doctor or go to urgent care within 24 hours (possible uveitis, iritis, or corneal infection).
Get seen today — urgent care or same-day visit
- Urgent
Red eye with thick, green or yellow discharge and crusting, especially if you wear contact lenses — see a clinician promptly (possible bacterial keratitis or corneal ulcer, which can threaten vision).
Get seen today — urgent care or same-day visit
When in doubt, err toward getting seen. These tiers are a general guide, not a substitute for a clinician's judgment about your specific situation.
Key facts
Allergic conjunctivitis affects up to 40% of the population in the United States, making it one of the most common causes of red, itchy eyes.
Dry eye syndrome affects an estimated 5-50% of people worldwide, depending on the population studied and diagnostic criteria used.
Acute angle-closure glaucoma is a medical emergency that can cause permanent vision loss within hours if not treated — it presents with a red, painful eye, blurred vision, halos around lights, and often nausea.
What's causing it
The same symptom can come from very different places. Here are the usual suspects for Eyes — the surface of the eye (conjunctiva, sclera, cornea) and surrounding structures (eyelids, tear ducts), tagged by mechanism and how common each one is — so you can see where an allergy actually fits.
Allergic conjunctivitis (eye allergies)
The most common cause of red, itchy, watery eyes. Allergens like pollen, dust mites, pet dander, or mold trigger the immune system to release histamine, causing blood vessels in the conjunctiva to dilate and become red. Both eyes are usually affected, and symptoms often occur seasonally or with known allergen exposure. Over-the-counter antihistamine eye drops can provide relief.
Dry eye syndrome
Insufficient tear production or poor-quality tears leads to dryness, irritation, and redness. It often feels like a gritty or burning sensation and worsens with screen use, dry air, or wind. Artificial tears (preservative-free) can help, but chronic dry eye may need prescription treatment from an eye doctor.
Viral or bacterial conjunctivitis (pink eye)
Infections of the conjunctiva cause redness with discharge — watery for viral, thicker and yellow-green for bacterial. Viral conjunctivitis often accompanies a cold and is highly contagious. Bacterial conjunctivitis may require antibiotic eye drops. Both can start in one eye and spread to the other.
Irritants and environmental factors
Smoke, chlorine in swimming pools, air pollution, dust, and prolonged screen time (reduced blinking) can irritate the eyes and cause redness. Contact lens overwear or poor lens hygiene is another common irritant cause. Removing the irritant and using lubricating drops usually resolves the redness.
Corneal abrasion or foreign body
A scratch on the cornea (abrasion) or a speck of dust, sand, or metal in the eye causes sudden redness, pain, tearing, and sensitivity to light. This is not an allergy and requires prompt medical evaluation to prevent infection or scarring. Do not rub the eye.
Uveitis or iritis (inflammation inside the eye)
Inflammation of the uvea (the middle layer of the eye) causes redness, pain, light sensitivity (photophobia), and sometimes blurred vision. It can be associated with autoimmune conditions (e.g., ankylosing spondylitis, sarcoidosis) or infections. Uveitis requires urgent evaluation by an ophthalmologist.
Where allergy actually fits in
When a symptom like this is allergy-driven, it usually points to a specific trigger. Knowing which one is the difference between guessing and actually fixing it.
Red eyes are very commonly caused by allergies — specifically allergic conjunctivitis. This occurs when airborne allergens (pollen, dust mites, pet dander, mold) trigger the immune system to release histamine in the eyes, causing redness, itching, tearing, and swelling. Allergic conjunctivitis typically affects both eyes and is often seasonal or tied to specific allergen exposure. It is not contagious. Over-the-counter antihistamine eye drops and oral allergy medications can provide relief. If you have red, itchy eyes that recur at certain times of the year or around specific triggers, allergy testing can help identify the cause and guide treatment, including immunotherapy (allergy shots or drops) for long-term relief.
Relief you can try at home
If your symptom is mild and you have no red-flag signs, these gentle steps often help. They soothe — they don't replace figuring out the cause.
- 1
Apply a cold compress
A clean, cool washcloth placed over closed eyes for 5-10 minutes can reduce redness and soothe itching from allergies. Do not share washcloths to avoid spreading infection.
- 2
Use artificial tears (preservative-free)
Over-the-counter lubricating eye drops can rinse away allergens and irritants and relieve dryness. Preservative-free drops are best for frequent use. Avoid drops that claim to 'get the red out' — they can cause rebound redness with overuse.
- 3
Try antihistamine eye drops for allergies
If itching is the main symptom, over-the-counter antihistamine eye drops (e.g., ketotifen) can block the allergic response. Use as directed and avoid touching the dropper tip to your eye.
- 4
Remove contact lenses and rest your eyes
If you wear contacts, remove them at the first sign of redness and switch to glasses until the redness resolves. Give your eyes a break from screens — follow the 20-20-20 rule: every 20 minutes, look at something 20 feet away for 20 seconds.
Stop any step that makes things worse. If the symptom isn't easing within a few days, check in with a clinician.
When to see a doctor
See a clinician or eye doctor if red eyes are accompanied by pain, light sensitivity, vision changes (blurring, halos, or vision loss), or a sensation of something in the eye after an injury. Redness with thick discharge, especially in contact lens wearers, needs prompt evaluation. Red eyes that persist for more than a week despite home care, or that recur frequently, should be evaluated to rule out chronic dry eye, allergies, or an underlying condition. Sudden severe pain with nausea or vomiting, or a chemical splash to the eye, requires emergency care.
❓Frequently Asked Questions
Itching is the hallmark of allergic conjunctivitis — if your eyes are red and intensely itchy, allergies are the most likely cause. Allergic eyes are also watery and usually affect both eyes at once. Infections (viral or bacterial conjunctivitis) tend to cause more of a gritty, burning sensation with discharge — watery for viral, thick and yellow-green for bacterial. Infections often start in one eye and may spread to the other, and they can be accompanied by cold symptoms (viral) or crusting on the lashes (bacterial).
Yes — dry eye syndrome is a very common cause of redness. When the eyes do not produce enough tears or the tears evaporate too quickly, the surface of the eye becomes irritated and the blood vessels dilate, causing redness. Dry eyes often feel gritty, burning, or 'tired,' and symptoms worsen with screen use, dry air, or wind. Artificial tears can help, but chronic dry eye may need prescription treatment from an eye doctor.
Go to the ER if red eyes are accompanied by severe pain (especially with nausea or vomiting), sudden vision loss, blurred vision, or seeing halos around lights. Also seek emergency care for a chemical splash to the eye, a visible foreign body that you cannot flush out, or an eye injury. These can signal acute glaucoma, a corneal ulcer, or other vision-threatening conditions.
Yes — contact lens overwear, poor lens hygiene, or sleeping in lenses not approved for overnight use can cause redness. This can range from simple irritation to serious infections like keratitis (corneal infection), which can threaten vision. If your eyes become red while wearing contacts, remove them immediately and switch to glasses. If redness persists or is accompanied by pain, discharge, or light sensitivity, see an eye doctor promptly.
It depends on the cause. Allergic conjunctivitis and dry eye are not contagious. Viral and bacterial conjunctivitis (pink eye) are highly contagious and can spread through direct contact with eye discharge or contaminated surfaces (towels, pillowcases, hands). If you have discharge or crusting, wash your hands frequently, avoid touching your eyes, and do not share towels or makeup until the infection clears.
Medically reviewed by
Dr. Chet TharpeMD
Last reviewed July 2026
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Read moreStop guessing which trigger is behind it
If your red eyes keeps coming back and an allergen might be the cause, testing tells you what you actually react to. Curex offers at-home allergy testing and immunotherapy so you can treat the trigger, not just soothe the symptom.
- At-home allergy test kit — no clinic visit
- Reviewed by board-certified allergists
- Find the trigger instead of guessing
This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. It cannot tell you what is causing your red eyes or whether it is an allergy. If you have any emergency sign — trouble breathing, fast-spreading swelling, sudden weakness or confusion, or severe pain — call 911 or go to the nearest emergency room. For anything that is new, worsening, or persistent, see a licensed healthcare provider. Curex offers at-home allergy testing and immunotherapy for confirmed environmental allergies; it does not diagnose this symptom or provide emergency care.