Most common cause of acute red eye
Viral infection is usual etiology
Viral<unk> 
Epidemic keratoconjunctivitis
Herpes zoster ophthalmicus
Herpes simplex keratitis
Bacterial<unk> 
Gonorrheal<unk> 
Chlamydia<unk> 
Allergic<unk> 
Caustic keratoconjunctivitis
Epidemic keratoconjunctivitis
Herpes zoster ophthalmicus
Herpes simplex keratitis
Gonorrheal<unk> 
Chlamydia<unk>
Conjunctivitis
Nontraumatic
Laryngitis
Acute angle-closure glaucoma^
Pharyngitis
Anterior uveitis
Sinusitis
Mastoiditis