Bacteria
Some cases are caused by bacteria, such as pneumococcus, staphylococcus or streptococcus, although allergies and some viruses can also cause conjunctivitis.
Virus
Other cases are caused by a virus called adenovirus. This virus can be spread in many ways including swimming pools, wet towels, etc.
Allergic Conjunctivitis
Some people are susceptible to allergic conjunctivitis brought on by use of drugs: (see info on drugs that harm the eyes for a more complete list of harmful drugs)
- Antibiotics - when antibiotics are given for eye problems topically they may have the side effect of causing an allergic conjunctivitis (red eye). Systemic antibiotics taken orally, intramuscularly, or intravenously to help with bacterial infections may cause some visual symptoms. For example:
- Synthetic penicillins (amoxicillin and ampicillin)- a person taking these may experience some mild redness of the eyes, itching and dry eyes. In rare cases they have been shown to cause hemorrhages of the blood vessels in the conjunctiva and in the retina
- Tetracycline - similar to the above plus light sensitivity and blurred vision
- Sulfonamides - many people are allergic to "sulfa drugs". This can cause blurred vision, light sensitivity and hemorrhages in the eye.
- Note Whenever taking antibiotics make sure you take probiotics such as acidophilus or bifidus and vitamin C to help ward off some of the side effects of the antibiotics.