Conjunctivitis

Introduction

Conjunctivitis, commonly called pink eye, is inflammation or infection of the conjunctiva—the transparent tissue covering the white of the eye and lining the inner eyelids. Inflamed tiny blood vessels make the eye look pink or red.

Causes include viruses, bacteria, allergies, a foreign body, or chemical splash. Viral and bacterial forms may affect one or both eyes and often accompany cold or sore-throat symptoms. Viral disease usually produces watery discharge; bacterial disease more often produces thicker yellow-green discharge.

Allergic conjunctivitis typically affects both eyes. Pollen and other allergens trigger inflammatory chemicals that cause intense itching, tearing, puffy lids, sneezing, and watery nasal discharge. Irritant conjunctivitis follows dust, smoke, chlorine, or chemicals—and sometimes the process of rinsing the eye itself.

Most cases improve with cause-specific care, hygiene, and time. Bacterial infection may need antibiotic drops or ointment; allergic disease responds to antihistamine or mast-cell–stabiliser drops; chemical injuries—especially acid or alkali—need emergency irrigation and urgent care. Because infectious forms spread easily, hand hygiene and avoiding shared towels matter.

Overview

Pink eye is one of the most common eye complaints across ages. Redness, itch, grit, watering, and morning crusting are typical.

Knowing the likely type—viral, bacterial, allergic, or irritant—guides treatment and isolation advice. Severe pain, marked light sensitivity, or reduced vision raises concern for corneal involvement and needs same-day review.

Lab tests are not routine; they are considered for severe, recurrent, treatment-resistant, or cornea-involving cases, and allergy testing may help when allergens are unclear.

• Inflammation of the conjunctiva causing pink or red eyes
• Main types: viral, bacterial, allergic, and irritant
• Watery vs thick yellow-green discharge helps suggest viral vs bacterial cause
• Allergic forms itch intensely and often come with nasal allergy symptoms
• Treatment depends on type—antibiotics are not for every case
• Infectious conjunctivitis is highly contagious without good hygiene

What happens in the body

When the conjunctiva is irritated by germs, allergens, or chemicals, blood vessels dilate and inflammatory fluid gathers on the eye surface. That produces redness, swelling, discharge, and the familiar gritty or burning feel.

Viruses and bacteria can spread by hand-to-eye contact and shared items. Allergens prompt antibody-driven release of histamine and related mediators. Chemicals and foreign bodies damage or inflame the surface directly until they are removed and the tissue recovers.

• Vessel dilation in the conjunctiva creates the pink appearance
• Infectious agents spread readily via hands and fomites
• Allergens trigger histamine-related itch and tearing
• Irritants and foreign bodies cause direct surface inflammation

Signs and symptoms

Symptoms vary by cause and severity. Common features include:

• Eye redness (one or both eyes)
• Itchiness
• Gritty or sandy sensation
• Watery eyes
• Burning sensation
• Blurred vision (often from discharge or tear-film disturbance)
• Increased light sensitivity
• Discharge that crusts overnight and may stick lashes together in the morning
• Viral pattern: watery discharge, often with cold or sore throat
• Bacterial pattern: thicker yellow-green discharge
• Allergic pattern: intense itching, both eyes, sneezing, watery nose

Causes and risk factors

Clinicians group causes to choose the right care:

• Viral infection (often highly contagious)
• Bacterial infection
• Allergens such as pollen, dust mites, or animal dander
• Foreign body in the eye
• Chemical splash or other irritants (smoke, chlorine, pollution)
• Associated upper respiratory infection symptoms with infectious types
• Eye rubbing and poor hand hygiene that spread infection
• Contact-lens overwear or poor lens hygiene (raises bacterial risk)

Diagnosis and evaluation

Diagnosis is usually clinical. Extra testing is selective:

• Symptom history: onset, one vs both eyes, discharge type, itch, contacts, chemicals, contact-lens use
• Eye examination of lids, conjunctiva, and cornea
• Swab of discharge for lab testing in severe, recurrent, non-responding, or cornea-involved cases
• Allergy evaluation when allergic conjunctivitis is suspected and triggers are unclear
• Urgent reassessment if pain is severe, vision drops, or a white corneal spot appears

Treatment and management

Match treatment to the type of conjunctivitis. Do not share leftover eye drops:

• Bacterial: antibiotic eye drops or ointment as prescribed—finish the course even if the eye looks better
• Viral: supportive care is often the mainstay; antivirals only when a clinician identifies a specific treatable viral cause
• Allergic: antihistamine and/or mast-cell–stabiliser drops; reduce allergen exposure
• Irritant: thorough rinsing with clean water or saline; seek emergency care immediately after acid or alkali injury
• Cool compresses and preservative-free lubricants for comfort when advised
• Stop contact-lens wear until cleared by an eye clinician
• Hygiene: wash hands, avoid touching eyes, do not share towels, pillowcases, or eye makeup

Prevention, self-care, and lifestyle

Not every condition is fully preventable, but the steps below may lower risk or recurrence:

• Wash hands often and avoid rubbing the eyes
• Do not share towels, cosmetics, or eye drops
• Replace eye makeup after infectious conjunctivitis as advised
• Stay home from school or work when highly contagious forms are active, per clinician guidance
• Manage allergies and keep indoor allergens down when allergic eye disease recurs
• Use protective eyewear for chemicals, dust, or splash risk at work
• Follow contact-lens cleaning and replacement schedules strictly

Possible complications

Delay, missed care, or unsafe self-medication can raise the chance of complications in some cases:

• Spread of infection to family members, classmates, or coworkers
• Prolonged discomfort, light sensitivity, and sleep disruption from crusting
• Corneal involvement in more severe infections, risking lasting vision problems if untreated
• Secondary bacterial infection after viral or irritant injury
• Contact-lens–related ulcers if lenses are worn during active disease

When to see a doctor or seek emergency care

Seek prompt medical advice or emergency care if any of the following apply—it is safer not to wait and see:

• Moderate to severe eye pain or strong light sensitivity
• Noticeable drop in vision
• Symptoms not improving as expected, or worsening on treatment
• Chemical splash—especially acid or alkali—after immediate irrigation
• Newborn or infant eye redness and discharge
• Immune compromise, recent eye surgery, or contact-lens pain with redness
• Repeated episodes that disrupt school, work, or sleep

Living with the condition

During an infectious episode, treat the home like a short isolation plan: separate towels, frequent handwashing, and cleaned pillowcases. Soft lighting and lubricating drops (if recommended) ease daily tasks.

For allergic pink eye, track seasons and triggers, keep windows managed during high pollen, and use prescribed drops early rather than waiting for peak itch.

Return to contact lenses only after clearance. If redness returns with lens use, stop lenses and get reviewed—do not push through pain.

Frequently asked questions

Is pink eye always contagious?

Viral and bacterial conjunctivitis are contagious. Allergic and many irritant forms are not. Hygiene still helps every type by reducing rubbing and secondary infection.

Do I always need antibiotic drops?

No. Antibiotics help bacterial disease. Viral and allergic conjunctivitis need different approaches. Unnecessary antibiotics will not speed viral recovery.

How can I tell viral from bacterial conjunctivitis?

Viral disease often has watery discharge and cold-like symptoms; bacterial disease more often has thicker yellow-green discharge. Overlap exists—examination is the safer way to decide treatment.

When are lab tests needed?

Most mild cases need none. Swabs or other tests are considered for severe, recurrent, treatment-resistant cases or when the cornea is involved.

Can allergies cause conjunctivitis?

Yes. Allergic conjunctivitis usually affects both eyes with strong itching and may come with sneezing and a watery nose. Antihistamine strategies and trigger control help.

What should I do after a chemical splash?

Rinse the eye immediately with plenty of clean water or saline and seek emergency care without delay—especially for acid or alkali exposure.

Important caution

This article is for general health education only. It is not personal medical advice or a substitute for an eye examination.

Use prescription eye medicines only as directed, and seek urgent care for pain, vision loss, or chemical injury.

If symptoms worsen or you are unsure which type of conjunctivitis you have, consult a qualified clinician promptly.