The surface tissues of the eye are [[colonized]] by [[normal flora]] such as ''[[streptococci]]'', ''[[staphylococci]]'', and ''[[corynebacteria]]''. Any change in the host defense or in the [[species of bacteria]] can lead to clinical infection. Any change in the flora can also occur by [[external contamination]] (contact lens wear, swimming) or spread from [[adjacent]] infectious sites (rubbing of the eyes).<ref name="pmid12564275">{{cite journal| author=Everitt H, Kumar S, Little P| title=A qualitative study of patients' perceptions of acute infective conjunctivitis. | journal=Br J Gen Pract | year= 2003 | volume= 53 | issue= 486 | pages= 36-41 | pmid=12564275 | doi= | pmc=1314490 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12564275 }} </ref>
The [[primary defense]] against infection is the [[epithelial]] layer covering the [[conjunctiva]]. [[Secondary defenses]] include [[hematologic immune mechanisms]] carried by the [[conjunctival]] [[vasculature]]; tear film [[immunoglobulins]] and [[lysozyme]]; and the rinsing action of [[lacrimation]] and blinking. [[Disruption]] of any of these [[defenses mechanisms]] can lead to infection.<ref name="pmid21188158">{{cite journal| author=Hutnik C, Mohammad-Shahi MH| title=Bacterial conjunctivitis. | journal=Clin Ophthalmol | year= 2010 | volume= 4 | issue= | pages= 1451-7 | pmid=21188158 | doi=10.2147/OPTH.S10162 | pmc=3000772 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21188158 }} </ref>
===[[Allergic Conjunctivitis]]===
Development of [[Allergic Conjunctivitis]] is result of [[type I hypersensitivity reactions]] involving the conjunctiva. Allergic conjunctivitis is prompted by [[IgE-mediated immediate hypersensitivity reaction]]. [[Mast cell]] play an important role in these allergic inflammations.<ref name="pmid26681960">{{cite journal| author=Kyei S, Koffuor GA, Ramkissoon P, Abokyi S, Owusu-Afriyie O, Wiredu EA| title=Possible Mechanism of Action of the Antiallergic Effect of an Aqueous Extract of Heliotropium indicum L. in Ovalbumin-Induced Allergic Conjunctivitis. | journal=J Allergy (Cairo) | year= 2015 | volume= 2015 | issue= | pages= 245370 | pmid=26681960 | doi=10.1155/2015/245370 | pmc=4657065 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26681960 }} </ref>
[[Airborne antigens]] may be involved in the pathogenesis of Allergic Conjunctivitis. Common [[airborne antigens]], include [[pollen]], grass, and weeds, may provoke the symptoms of acute Allergic Conjunctivitis, and also there is a strong association with [[atopic dermatitis]] and [[Allergic Conjunctivitis]].<ref name="pmid19134019">{{cite journal| author=Malling HJ, Montagut A, Melac M, Patriarca G, Panzner P, Seberova E et al.| title=Efficacy and safety of 5-grass pollen sublingual immunotherapy tablets in patients with different clinical profiles of allergic rhinoconjunctivitis. | journal=Clin Exp Allergy | year= 2009 | volume= 39 | issue= 3 | pages= 387-93 | pmid=19134019 | doi=10.1111/j.1365-2222.2008.03152.x | pmc=4233960 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19134019 }} </ref><ref name="pmid17967188">{{cite journal| author=Kämpe M, Stålenheim G, Janson C, Stolt I, Carlson M| title=Systemic and local eosinophil inflammation during the birch pollen season in allergic patients with predominant rhinitis or asthma. | journal=Clin Mol Allergy | year= 2007 | volume= 5 | issue= | pages= 4 | pmid=17967188 | doi=10.1186/1476-7961-5-4 | pmc=2174506 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17967188 }} </ref>
Combination of type I and [[type IV hypersensitivity reactions]] may be responsible for the pathogenesis of [[Giant papillary conjunctivitis]]. It is believed that an [[antigen]] is present, in predisposed individuals, which stimulates the immunological reaction.Prolonged mechanical irritation to the superior tarsal conjunctiva, of the upper lid, from any of a variety of foreign bodies may also be a contributing factor in Giant papillary conjunctivitis.
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Pathophysiology
Infective Conjunctivitis is spread from:
Direct contact with the infected person’s eye drainage or drainage from the person’s cough, sneeze, or runny nose
Contact with the infected person’s fingers, hands or objects that may have the infected person’s drainage on them (e.g. eye makeup applicators, towels, shared eye medications)
