A red eye can have several causes, from seasonal allergies and irritation to conjunctivitis (often called pink eye) and conditions that need prompt medical attention. The symptoms can overlap, so the color of your eye—or the appearance of discharge—cannot reliably tell you what is causing the problem.

Itching in both eyes may point toward allergies, while watery discharge can occur with viral conjunctivitis and sticky discharge may occur with bacterial conjunctivitis. But these are clues, not a diagnosis. This guide explains common patterns, practical steps, and warning signs that should not be ignored. If you have eye pain, reduced vision, significant light sensitivity, an eye injury, or a red eye while wearing contact lenses, seek prompt professional assessment.

Red eye, pink eye and allergies at a glance

Possible cause	Common pattern	Contagious?	Important note
Eye allergies (allergic conjunctivitis)	Often intense itching, watery eyes, puffiness, and symptoms in both eyes; sneezing or an itchy nose may also occur.	No. Allergies do not spread person to person.	Exposure to pollen, dust mites, pet dander, mold, or other allergens may trigger symptoms.
Viral conjunctivitis	Redness, watery discharge, irritation or a gritty feeling; may occur with a cold and can start in one eye before affecting the other.	Often yes.	Antibiotics do not treat viral infections.
Bacterial conjunctivitis	Redness and discharge that may be thicker or sticky; eyelids may be stuck together after sleep.	Can be.	Discharge appearance alone cannot confirm a bacterial cause or determine whether antibiotics are needed.
Dry eye or irritation	Burning, grittiness, watering, or fluctuating blur; symptoms may relate to wind, screens, smoke, or dry environments.	Usually no.	Persistent redness, pain, or vision changes needs assessment.
Other eye conditions or injury	May include marked pain, light sensitivity, sudden vision changes, or a very red eye.	Depends on the cause.	Do not assume these symptoms are ordinary pink eye or allergies.

This comparison is for general education only. Several conditions share symptoms, and more than one factor may be present at the same time. An eye-care professional can assess your history and examine your eyes to help identify the cause.

What does “pink eye” mean?

Pink eye is the everyday name for conjunctivitis, inflammation of the conjunctiva—the thin, clear tissue covering the white of the eye and lining the inside of the eyelids. The inflammation makes small blood vessels more visible, causing a pink or red appearance. Conjunctivitis may be caused by viruses, bacteria, allergens, or irritants; not every red eye is conjunctivitis.

Viral and bacterial conjunctivitis can spread between people. Allergic conjunctivitis is a reaction to an allergen and is not contagious. Irritation from smoke, chemicals, a foreign body, or contact-lens problems can also cause redness without being a contagious infection.

For an evidence-based overview of symptoms and causes, read the CDC’s pink eye information. The Centers for Disease Control and Prevention notes that symptoms can vary depending on the cause.

How eye allergies may present

Allergic conjunctivitis often causes prominent itching, watering, redness, and puffy eyelids. Both eyes are commonly affected, although symptoms may not be identical. You may also have sneezing, a runny or itchy nose, or other allergy symptoms. Symptoms can appear after contact with pollen, dust mites, animal dander, mold, or another trigger.

A strong urge to rub the eyes is common with allergies, but rubbing can worsen irritation. If you suspect an allergy, avoid the likely trigger where practical and consider a clean, cool compress for comfort. Artificial tears may help wash away irritants and relieve dryness for some people. Ask a pharmacist or clinician about appropriate allergy treatments, especially if you use other medicines, wear contact lenses, or have ongoing symptoms.

Do not assume that itching proves the cause is an allergy. Infection and other eye problems can overlap with allergy symptoms. New, severe, persistent, or one-sided symptoms deserve attention, particularly if there is pain, light sensitivity, or a change in vision.

Lumiere Optique’s local page provides more information about eye allergy relief in Scottsdale. Have a qualified eye-care professional confirm which services are appropriate for your symptoms.

How viral and bacterial conjunctivitis can differ

Viral conjunctivitis

Viral conjunctivitis commonly causes redness, watering, burning, or a gritty sensation. It may occur during or after a respiratory illness, and one eye may become affected before the other. Many uncomplicated cases improve without specific antiviral treatment, but recovery can take days to a few weeks depending on the cause. Some viral infections require medical treatment, so worsening or unusual symptoms should be assessed.

Because viral conjunctivitis can be contagious, wash your hands regularly, avoid touching your eyes, do not share towels or eye cosmetics, and clean frequently touched surfaces. Use separate clean tissues or cloths to wipe away discharge, and wash your hands afterward.

Bacterial conjunctivitis

Bacterial conjunctivitis may cause red eyes with mucus or pus-like discharge, sometimes leaving the eyelids sticky after sleep. However, discharge color or thickness is not enough to diagnose a bacterial infection. Some cases improve without antibiotics, while others may benefit from prescription treatment. A clinician can decide whether medication is appropriate based on the examination and the person’s circumstances.

Do not use leftover antibiotic eye drops or someone else’s medication. Antibiotics do not treat viral conjunctivitis or allergies, and unnecessary use may delay appropriate care. Seek professional advice if discharge is substantial, symptoms are worsening, or you are unsure of the cause.

The American Academy of Ophthalmology’s pink eye guide explains the main types of conjunctivitis, how they differ, and why treatment depends on the cause.

Other important causes of red eyes

Redness can also result from dry eye, eyelid inflammation, contact-lens irritation, a foreign body, a scratched cornea, or exposure to smoke, dust, fumes, or chemicals. A small burst blood vessel can cause a sharply defined red patch on the white of the eye. Other conditions, including inflammation inside the eye or certain pressure-related emergencies, can cause a painful red eye and threaten vision.

The right next step depends on the full symptom pattern and circumstances. Mild irritation without pain or vision changes may settle, but a new or persistent red eye should not automatically be attributed to allergies, screen use, or tiredness. If symptoms are severe, sudden, or getting worse, seek medical care.

For a broader overview of red-eye causes and warning signs, see the NHS red-eye guidance.

Contact lenses and higher-risk symptoms

A red eye in someone who wears contact lenses deserves particular caution. Contact-lens wear can be associated with corneal infections, which can threaten sight if not treated promptly. Remove your lenses and seek urgent advice from an eye-care professional if your eye is red, painful, unusually sensitive to light, or your vision changes. Do not put the lenses back in until a clinician says it is safe.

Avoid sleeping in lenses unless they were specifically prescribed for that use and you have been advised on the risks. Follow lens-cleaning instructions, use the recommended solution, replace lenses and cases as directed, and never rinse lenses with tap water or saliva. Good lens hygiene lowers risk but does not rule out an infection when symptoms occur.

Contagion and safe hygiene guidance

Not every red eye is contagious. Allergic conjunctivitis and irritation from environmental triggers do not spread from person to person, while viral and bacterial conjunctivitis may. Since the cause is not always obvious, basic hygiene is sensible when redness and discharge begin.

• Wash your hands with soap and water before and after touching the area around your eyes.
• Do not share towels, pillowcases, eye makeup, or eye drops.
• Avoid rubbing your eyes, and use clean tissues or cloths to remove discharge.
• Clean frequently touched surfaces and follow workplace or school guidance if an infectious condition is suspected.
• Pause contact-lens use during symptoms and follow professional advice before restarting.
• Do not use eye drops prescribed for another person or reuse old prescription medication.

If you may have infectious conjunctivitis, take extra care around other people, especially those who are vulnerable. Ask a clinician about returning to school or work if symptoms are significant or you cannot avoid close contact.

Red flags requiring urgent assessment

Get prompt, same-day professional advice for a red eye accompanied by eye pain, pronounced light sensitivity, reduced or blurred vision that does not clear after wiping away discharge, intense redness, or symptoms that are worsening. Contact-lens wearers with a red eye should be assessed urgently, particularly if there is pain or a vision change.

Seek emergency care for sudden vision loss, severe eye pain, a significant eye injury, a chemical splash, or a red eye with severe headache and nausea. If a chemical enters the eye, begin rinsing immediately with plenty of clean running water while arranging emergency help; do not delay rinsing to search for instructions. Do not try to remove an embedded object yourself.

A newborn with a red or sticky eye needs prompt medical assessment. People with weakened immune systems or recent eye surgery should also seek advice early when new eye symptoms develop.

Do not wait for a routine appointment if you have warning signs. These symptoms can indicate problems more serious than routine conjunctivitis or allergies.

What an eye examination can establish

An eye-care professional will consider when symptoms began, whether one or both eyes are affected, the presence of itching, pain, discharge or light sensitivity, recent illness, allergy exposure, contact-lens use, injury, and relevant medical history. The clinician may examine the eyelids and surface of the eye and assess vision. Additional testing may be needed in some cases.

The purpose is not simply to label an eye as “pink eye.” Identifying the likely cause helps guide care and reduces the risk of using an ineffective treatment. For example, antibiotics are not useful for allergy-related or viral conjunctivitis, while certain painful red-eye conditions require urgent treatment.

If you are in Scottsdale, Arizona, you can review Lumiere Optique’s eye-care services to learn about the practice. For non-emergency concerns, use its appointment request page to ask about an appropriate assessment. The practice should confirm available clinicians and services. Urgent symptoms need prompt medical care rather than waiting for a routine appointment.

Frequently asked questions

Is red eye always contagious?

No. Redness may be caused by allergies, dry eye, irritation, injury, or other conditions that are not contagious. Viral and bacterial conjunctivitis can spread. Because symptoms overlap, use good hygiene and seek advice when the cause is uncertain.

Can allergies cause discharge?

Yes. Allergic conjunctivitis often causes watery tears. Itching and symptoms in both eyes may support an allergy pattern, especially alongside sneezing or an itchy nose. However, discharge can occur in several conditions, so it cannot establish the diagnosis by itself.

Should I wear contacts with a red eye?

No—pause contact-lens use while the eye is red or irritated. A red eye in a contact-lens wearer can indicate a potentially serious corneal problem, particularly when accompanied by pain, light sensitivity, or blurred vision. Seek urgent professional advice and wait until you are told it is safe to resume wearing lenses.

What if I have pain or sensitivity to light?

Eye pain or light sensitivity should not be treated as routine allergy symptoms. Seek prompt professional assessment, especially if the eye is very red, vision is affected, or symptoms are worsening. Severe pain or sudden vision loss requires emergency care.

When should I seek urgent treatment?

Seek same-day care for a painful red eye, light sensitivity, reduced vision, intense redness, worsening symptoms, or a red eye while wearing contact lenses. Sudden vision loss, severe pain, chemical exposure, or a serious injury requires emergency care.

Can I use antibiotic drops for pink eye?

Only use antibiotic eye drops when they have been prescribed or recommended for you by a qualified clinician. Pink eye may be viral, bacterial, allergic, or irritation-related, and antibiotics do not treat every cause. The correct treatment depends on an assessment.

The bottom line

Itchy, watery eyes—especially when both eyes are affected—can fit an allergy pattern. Viral conjunctivitis often causes watery redness and may occur with a cold, while bacterial conjunctivitis may cause sticky discharge. But these patterns overlap, and discharge color or redness alone cannot reliably diagnose the cause.

Avoid rubbing your eyes, practise careful hand hygiene, and stop wearing contact lenses while symptoms are present. Arrange an assessment for persistent or worsening redness, and seek prompt care for pain, light sensitivity, vision changes, injury, or a red eye in a contact-lens wearer. A qualified professional can help determine the cause and recommend the safest next step.