Pink Eye vs. Allergies: How to Tell the Difference

Your eye is red, it waters, and it will not stop bothering you. Is it pink eye, or is it allergies? The two look alike at a glance, but they have different causes, one of them spreads to other people and the other does not, and the eye drops that fix one do nothing for the other. Getting it wrong means a week of the wrong treatment.

Here is the fastest way to tell them apart, the early signs of each, what to do for kids, and when red eyes need a doctor rather than a pharmacy.

Pink eye vs allergies at a glance

Both conditions are a form of conjunctivitis, which just means the thin clear layer over the white of the eye is inflamed. The difference is what inflamed it. Use this table first, then read the sections below for the detail.

Two questions settle most cases. Did it start in both eyes at once, and is itching the main complaint? If yes to both, it is almost always allergies. If it started in one eye, feels gritty rather than itchy, and you have or recently had a cold, it is almost always viral pink eye. Thick colored discharge every morning means bacterial pink eye until proven otherwise.

What eye allergies look like

Allergic conjunctivitis is your immune system overreacting to something harmless, most often pollen, pet dander, dust mites, or mold. When the allergen lands on the eye, cells in the conjunctiva release histamine, and histamine is what makes the eye itch, water, and swell. Because allergens land on both eyes, both react together.

The giveaways are itching that makes you want to rub constantly, puffy lids, watering, and a clear stringy mucus you might notice in the corner of the eye. Most people also have the nose symptoms of hay fever at the same time. Symptoms follow the trigger. Spring and fall for tree, grass, and weed pollen, all year round for dust mites and pets, or within minutes of visiting a house with a cat. The NHS notes that allergic conjunctivitis is not infectious, so there is nothing to catch and nothing to keep children home from school for.

Rubbing makes it worse. It releases more histamine, and it can scratch the surface of the eye or introduce bacteria, which is how an allergy episode occasionally turns into a real infection.

What pink eye looks like

When people say pink eye, they usually mean infectious conjunctivitis, caused by a virus or bacteria. The National Eye Institute describes it as one of the most common eye problems in both children and adults.

Viral pink eye

This is the most common kind, and it usually comes from the same adenoviruses that cause colds. It often starts a few days into a cold or sore throat, in one eye, with watering, redness, a gritty or burning feeling, and mild crusting in the morning. It frequently spreads to the second eye within a couple of days. It is very contagious through hands, towels, and pillowcases, and there is no cure. It clears on its own in one to two weeks, occasionally three. Antibiotics do nothing for it.

Bacterial pink eye

Bacterial infection produces the thick yellow or green discharge that pink eye is famous for. The lashes are often matted shut when you wake up, and the eye feels sore and sticky rather than itchy. It is more common in children than adults. Antibiotic drops or ointment shorten it to a few days and reduce the time you are contagious, though mild cases often clear without them.

Early stage pink eye symptoms

Many searches ask what pink eye looks like in the first day, before the obvious discharge. Early signs are a pink tinge to the white of one eye, a feeling that something is in the eye, watering, mild sensitivity to light, and a little crust at the lashes in the morning. If you or your child had a cold in the past week, assume it is viral and start the hygiene steps below right away, because that first day or two is when it spreads most easily.

Pink eye vs allergies in kids and toddlers

Young children cannot tell you whether their eye itches or burns, so parents have to read the other clues. The American Academy of Ophthalmology has a useful overview of conjunctivitis in children and adults. In practice:

• Both eyes red, rubbing constantly, sneezing, clear runny nose, worse outdoors: almost certainly allergies. Common from about age 3 onward and often runs in families.
• One goopy eye, crusted shut in the morning, after a cold or alongside an ear infection: bacterial pink eye. This is the most common type in toddlers and preschoolers.
• One or both watery red eyes with a cold, a cough, or a fever: viral pink eye.
• A newborn with red, swollen, or discharging eyes: see a doctor the same day. Eye infections in the first month can be serious.

On school and daycare: allergic eyes never need to stay home. For infectious pink eye, policies vary. Many schools ask that a child with bacterial pink eye has had 24 hours of antibiotic drops before returning, and that a child with viral pink eye stays home while the eye is actively watering and crusting. Check your school's rule, and in the meantime teach the one habit that matters most, which is keeping hands away from the face and washing them often.

How to treat each one

Eye allergies

• Antihistamine and mast cell stabilizer eye drops. Ketotifen and olopatadine are sold over the counter in the US and work within minutes. Use them daily through the season rather than only when the eyes flare.
• Oral antihistamines such as cetirizine or loratadine help when the nose is involved too, though they can dry the eyes a little.
• Cold compresses and artificial tears calm itching and rinse pollen off the surface of the eye.
• Cut exposure. Keep windows closed on high pollen days, shower and change after being outside, wash bedding hot, and keep pets out of the bedroom.
• Skip redness-relief drops with naphazoline or tetrahydrozoline for more than a few days. They cause rebound redness.

Viral pink eye

There is no medicine that clears it faster. Cool compresses, preservative-free artificial tears, and time are the treatment. Antibiotic drops do not help and are a common reason people wrongly think they are "immune" to antibiotics later. Wash hands often, use a fresh towel and pillowcase each day, throw away eye makeup you used while infected, and stay out of swimming pools until it has cleared.

Bacterial pink eye

A doctor or, in some states, a pharmacist can prescribe antibiotic drops or ointment. Symptoms usually improve within two to three days. Finish the course. Wipe crusts away with a clean cotton pad soaked in cooled boiled water, from the inner corner outward, using a new pad for each eye.

Contact lens wearers

Take the lenses out at the first sign of a red eye and switch to glasses until it is fully better. Throw away the lenses and the case you were using. Red eye in a contact lens wearer can occasionally be a corneal infection, which can damage sight quickly, so if there is any pain or blurred vision, see an eye doctor the same day rather than waiting it out.

When to see a doctor

Most red eyes are harmless and settle within a week or two. See a doctor promptly, the same day if possible, if you have any of the following, because they can point to something more serious than conjunctivitis:

• Moderate or severe eye pain, rather than irritation
• Sensitivity to light that makes you squint or close the eye
• Blurred vision that does not clear when you blink the discharge away
• Intense redness, or redness that is mostly in a ring around the colored part of the eye
• Symptoms in a newborn, in a contact lens wearer, or in someone with a weakened immune system
• Thick discharge that is getting worse after two days of antibiotic drops
• Symptoms lasting more than two weeks

A doctor can usually tell allergy from infection by looking, and can check that the cornea is not involved.

Can allergies turn into pink eye?

Allergic conjunctivitis is, strictly speaking, a type of pink eye, which is where a lot of the confusion starts. But allergies do not turn into an infection on their own. What happens is that constant rubbing breaks down the eye's surface defenses and carries bacteria from the hands into the eye, and a bacterial infection sets up on top of the allergy. If an itchy, watery allergic eye suddenly produces thick yellow discharge, treat it as bacterial pink eye and see a doctor for drops.

The bottom line

Allergies itch, affect both eyes together, come with sneezing, and are not contagious. Pink eye starts in one eye, feels gritty or sticky, often follows a cold or produces colored discharge, and spreads easily. Match the treatment to the cause: antihistamine drops for allergies, patience and hygiene for viral pink eye, antibiotic drops for bacterial pink eye. And if there is real pain, light sensitivity, or blurred vision, stop guessing and get the eye looked at.

Frequently asked questions