Conjunctivitis, often called pink eye, is inflammation of the conjunctiva, the thin clear tissue that covers the white part of the eye and lines the inside of the eyelid. CDC says pink eye is one of the most common and treatable eye conditions, and NHS notes that it is also known as red or pink eye. Viral and bacterial forms can be very contagious.

This matters because not every red eye is harmless, and not every case is the same. Some conjunctivitis is caused by viruses or bacteria, while allergic conjunctivitis is not contagious. Symptoms may be mild, but certain warning signs mean it should not be managed as a routine irritation.

Conjunctivitis is inflammation of the outer layer of the eye, especially the conjunctiva. NHS says it usually affects both eyes and commonly makes them red, itchy, watery, gritty, or sticky. CDC says symptoms often include redness or swelling of the white of the eye or inner eyelid.

That is important because pink eye is not defined by redness alone. The full picture often includes discharge, irritation, crusting, itchiness, or swelling, depending on the cause.

Official sources describe a very consistent group of common symptoms. NHS says conjunctivitis usually causes: red eyes; burning or a gritty feeling; pus that sticks to the eyelashes; itching; watering.

CDC and Mayo Clinic list a similar pattern, including redness, swelling, itchiness, discharge that forms crust overnight, tearing, and sometimes light sensitivity.

One of the most noticeable signs is discharge that makes the eyelids sticky, especially in the morning. NHS says conjunctivitis can produce pus that sticks to the lashes, and Mayo Clinic says discharge may form a crust during the night that can make it hard to open the eyes in the morning.

This matters because a sticky, crusting eye is more suggestive of infective conjunctivitis than a simple temporary irritation.

Not all conjunctivitis is infectious. CDC's clinical overview says allergic conjunctivitis is not contagious, and it is common in people who also have hay fever, asthma, or eczema. NHS child and community guidance also links itchiness strongly with allergic conjunctivitis.

That means itchiness can be an important clue, especially when both eyes are involved and there are other allergy symptoms too.

CDC says pink eye caused by viruses and bacteria is very contagious, and NHS notes that conjunctivitis producing sticky pus is contagious. CDC prevention material also advises avoiding rubbing the eyes and not sharing towels, makeup, eye drops, contact lens items, or bedding.

This is one of the most practical points: some forms of pink eye spread easily through hands, shared items, and close contact, so hygiene matters.

Conjunctivitis may involve one eye or both. Mayo Clinic says symptoms can affect one or both eyes, and NHS notes that conjunctivitis usually affects both eyes, though not always exactly equally.

That means a red eye in just one eye does not rule it out, and both-eye redness does not automatically tell you which type it is.

This is important. Mayo Clinic's red-eye guidance says some red eyes need immediate medical attention, especially when there is sudden vision change, significant pain, fever, light sensitivity, vomiting, swelling, or inability to keep the eye open.

So while conjunctivitis is common, a red eye should not automatically be assumed to be simple pink eye if more serious symptoms are present.

CDC says it is important to seek medical care for pink eye in some situations. Its treatment page says to seek care if you have pink eye along with symptoms such as: eye pain; light sensitivity; blurred vision that does not improve when discharge is wiped away; intense redness; symptoms that get worse or do not improve.

Mayo Clinic sources add similar warning signs, including more than mild eye pain, blurry vision that does not clear, vision loss, worsening symptoms after several days, or warm red swelling extending beyond the eyelid.

These warnings matter because eye pain and visual symptoms are not typical 'nothing to worry about' pink-eye features.

CDC says newborns with symptoms of pink eye should see a doctor right away.

This is especially important because red eye with discharge in a newborn is treated much more seriously than routine conjunctivitis in older children or adults.

Sensitivity to light, also called photophobia, may happen with conjunctivitis, but it is also a warning sign if it is strong or associated with other symptoms. Mayo Clinic lists light sensitivity among possible symptoms, and both CDC and Mayo's red-eye guidance treat painful light sensitivity as something that deserves more caution.

That means a mildly gritty eye is different from a red eye that hurts, blurs vision, and cannot tolerate light.

'Every red eye is just pink eye.' Not true. Mayo Clinic says red eye with pain, vision change, severe headache, fever, swelling, or vomiting needs more urgent medical attention.

'If it's itchy, it must be infectious.' Not necessarily. CDC says allergic conjunctivitis is not contagious and is common in people with other allergic conditions.

'If there's discharge, it's always minor.' False. Discharge is common in conjunctivitis, but blurred vision, eye pain, worsening swelling, or failure to improve should not be ignored.

'Pink eye is always harmless and never needs a doctor.' Also false. CDC specifically says some cases do need medical care, and newborns with symptoms should be seen right away.

Conjunctivitis is a common eye condition that usually causes redness, watering, discharge, itchiness, and a gritty feeling. Official sources from NHS, CDC, and Mayo Clinic all show the same core pattern: viral and bacterial pink eye can be contagious, allergic conjunctivitis is not contagious, and warning signs such as eye pain, light sensitivity, blurred vision, worsening symptoms, or newborn symptoms need medical attention.

The safest bottom line is simple: pink eye is common, but a red eye with pain, vision changes, strong light sensitivity, or worsening swelling should never be brushed off as 'just conjunctivitis.'

*This article is for informational purposes only and does not replace professional medical advice. Always consult a healthcare provider for conjunctivitis diagnosis and treatment.*