From the Guidelines
Pink eye, or conjunctivitis, is commonly caused by viral infections, bacterial infections, allergies, and irritants, with the most common causes including dry eye, blepharitis, and allergic conjunctivitis, as stated in the conjunctivitis preferred practice pattern 1. The causes of conjunctivitis can be classified into noninfectious and infectious types, with noninfectious types including allergic, mechanical/irritative/toxic, immune-mediated, and neoplastic, and infectious types including viral and bacterial conjunctivitis 1. Some of the specific causes of conjunctivitis include:
- Allergic conjunctivitis, which results from allergens like pollen or pet dander and can be managed with antihistamine eye drops such as ketotifen (Zaditor) or olopatadine (Pataday) 1
- Viral conjunctivitis, often caused by adenoviruses, which is highly contagious and typically resolves on its own within 1-2 weeks 1
- Bacterial pink eye, frequently caused by Staphylococcus aureus or Streptococcus pneumoniae, which can be treated with antibiotic eye drops like erythromycin or ciprofloxacin, usually prescribed for 5-7 days 1
- Irritant conjunctivitis, which occurs from exposure to chemicals, smoke, or foreign objects 1
- Dry eye and blepharitis, which are the most frequent causes of conjunctival inflammation, and require treatment directed at correcting the underlying problems 1. It is essential to differentiate between primary conjunctival disease and conditions in which conjunctival inflammation is secondary to systemic or ocular diseases, and to address the underlying systemic disease or condition when treating conjunctivitis 1.
From the FDA Drug Label
AzaSite is used to treat bacterial conjunctivitis which is an infection of the eye caused by certain bacteria. Bacterial conjunctivitis is a bacterial infection of the mucous membranes which line the inside of the eyelids. Symptoms may include redness of the eye and discharge. The infection can be spread to other people and to both eyes.
The common causes of conjunctivitis (pink eye) are bacterial infections.
- The specific bacteria that can cause conjunctivitis include:
- Corynebacterium species
- Micrococcus luteus
- Staphylococcus aureus
- Staphylococcus epidermidis
- Staphylococcus haemolyticus
- Staphylococcus hominis
- Staphylococcus warneri
- Streptococcus pneumoniae
- Streptococcus viridans group
- Acinetobacter lwoffii
- Haemophilus influenza
- Haemophilus parainfluenzae
- Chlamydia trachomatis 2 3
From the Research
Causes of Conjunctivitis
The common causes of conjunctivitis (pink eye) can be categorized into several types, including:
- Viral conjunctivitis: the most common overall cause of conjunctivitis, usually does not require treatment 4, 5, 6
- Bacterial conjunctivitis: the second most common cause of infectious conjunctivitis, often presents with purulent discharge and mattering of the eyelids 4, 5, 7, 8
- Allergic conjunctivitis: encountered in up to 40% of the population, characterized by itching, mucoid discharge, chemosis, and eyelid edema 4, 5, 7, 6
- Conjunctivitis secondary to sexually transmitted diseases: such as chlamydia and gonorrhea, requires systemic treatment in addition to topical antibiotic therapy 4, 7
- Toxic conjunctivitis: caused by long-term usage of eye drops with preservatives 6
- Other causes: including foreign bodies and non-allergic environmental causes 8
Characteristics of Each Type
Each type of conjunctivitis has distinct characteristics, such as:
- Viral conjunctivitis: typically presents with watery discharge, burning, gritty feeling 5, 8
- Bacterial conjunctivitis: typically presents with mucopurulent discharge, mattering of the eyelids 5, 8
- Allergic conjunctivitis: typically presents with bilateral itching, watery discharge 5, 8
- Conjunctivitis secondary to sexually transmitted diseases: typically presents with severe, bilateral, purulent conjunctivitis 4, 7