| Bacterial |
| Hyperacute (purulent) |
| Neisseria gonorrhoeae |
| Neisseria meningitidis |
| Neisseria gonorrhoeae subspecies kochii |
| Acute (mucopurulent) |
| Pneumococcus (Streptococcus pneumoniae) (temperate climates) |
| Haemophilus aegyptius (Koch-Weeks bacillus) (tropical climates) |
| Subacute |
| Haemophilus influenzae (temperate climates) |
| Chronic, including blepharoconjunctivitis |
| Staphylococcus aureus |
| Moraxella lacunata (diplobacillus of Morax-Axenfeld) |
| Rare types (acute, subacute, chronic) |
| Streptococci |
| Moraxella catarrhalis |
| Coliforms |
| Proteus |
| Corynebacterium diphtheriae |
| Mycobacterium tuberculosis |
| Chlamydial |
| Trachoma (C trachomatis serovars A–C) |
| Inclusion conjunctivitis (C trachomatis serovars D–K) |
| Lymphogranuloma venereum (LGV) (C trachomatis serovars L1–3) |
| Viral |
| Acute viral follicular conjunctivitis |
| Pharyngoconjunctival fever due to adenoviruses types 3 and 7 and other serotypes |
| Epidemic keratoconjunctivitis due to adenovirus types 8 and 19 |
| Herpes simplex virus |
| Acute hemorrhagic conjunctivitis due to enterovirus type 70; rarely, coxsackievirus type A24 |
| Chronic viral follicular conjunctivitis |
| Molluscum contagiosum virus |
| Viral blepharoconjunctivitis |
| Varicella, herpes zoster due to varicella-zoster virus |
| Measles virus |
| Rickettsial (rare) |
| Nonpurulent conjunctivitis with hyperemia and minimal infiltration, often a feature of rickettsial diseases |
| Typhus |
| Murine typhus |
| Scrub typhus |
| Rocky Mountain spotted fever |
| Mediterranean fever |
| Q fever |
| Fungal (rare) |
| Ulcerative or granulomatous |
| Candida |
| Granulomatous |
| Rhinosporidium seeberi |
| Coccidioides immitis (San Joaquin Valley fever) |
| Sporothrix schenckii |
| Parasitic (rare but important) |
| Chronic conjunctivitis and blepharoconjunctivitis |
| Thelazia californiensis |
| Loa loa |
| Ascaris lumbricoides |
| Trichinella spiralis |
| Schistosoma haematobium (bladder fluke) |
| Taenia solium (cysticercus) |
| Pthirus pubis (Pediculus pubis, public louse) |
| Fly larvae (Oestrus ovis, etc) (ocular myiasis) |
| Immunologic (allergic) |
| Immediate (humoral) hypersensitivity reactions |
| Hay fever conjunctivitis (pollens, grasses, animal danders, etc) |
| Vernal keratoconjunctivitis |
| Atopic keratoconjunctivitis |
| Giant papillary conjunctivitis |
| Delayed (cellular) hypersensitivity reactions |
| Phylctenulosis |
| Mild conjunctivitis secondary to contact blepharitis |
| Autoimmune disease |
| Primary and secondary Sjögren's syndrome |
| Mucous membrane pemphigoid |
| Chemical or irritative |
| Latrogenic |
| Idoxuridine, brimonidine, apraclonidine, dipivefrin, and other topically applied drugs |
| Preservatives in eye drops |
| Contact lens solutions, particularly their preservatives |
| Occupational |
| Acids |
| Alkalies |
| Smoke |
| Wind |
| Ultraviolet light |
| Caterpillar hair |
| Etiology unknown |
| Folliculosis |
| Chronic follicular conjunctivitis (Orphan's conjunctivitis, Axenfeld's conjunctivitis) |
| Ocular rosacea |
| Psoriasis |
| Stevens–Johnson syndrome, toxic epidermal necrolysis, and erythema multiforme |
| Dermatitis herpetiformis |
| Epidermolysis bullosa |
| Superior limbic keratoconjunctivitis |
| Ligneous conjunctivitis |
| Reiter's syndrome |
| Mucocutaneous lymph node syndrome (Kawasaki disease) |
| Associated with systemic disease |
| Thyroid disease (exposure, congestive) |
| Gouty conjunctivitis |
| Carcinoid conjunctivitis |
| Sarcoidosis |
| Tuberculosis |
| Syphilis |
| Secondary to dacryocystitis or canaliculitis |
| Conjunctivitis secondary to dacryocystitis pneumococci or beta-hemolytic streptococci |
| Conjunctivitis secondary to canaliculitis Actinomyces israelii, Candida species Aspergillus species (rarely) |