healing properties) Eye drops (A reaction to preservatives in eye drops can cause toxic conjunctivitis) Contact lens solution (some preservatives can irritate the eye over time resulting in conjunctivitis) Contact lens (conjunctivitis is also caused by repeated mechanical irritation of the conjunctiva by contact lens wearers) Most cases of seasonal conjunctivitis are due to pollen and occur in the hay fever season, grass pollens in early summer and various other pollens and moulds may cause symptoms later in the summer. Pathophysiology The ocular allergic response is a cascade of events that is coordinated by mast cells. Beta chemokines such as eotaxin and MIP-1 alpha have been implicated in the priming and activation of mast cells in the ocular surface. When a particular allergen is present, sensitization takes place and prepares the system to launch an antigen specific response. TH2 differentiated T cells release cytokines, which promote the production of antigen specific immunoglobulin E (IgE). IgE then binds to IgE receptors on the surface of mast cells. Then, mast cells release histamine, which then leads to the release of cytokines, prostaglandins, and platelet-activating factor. Mast cell intermediaries cause an allergic inflammation and symptoms through the activation of inflammatory cells. When histamine is released from mast cells, it binds to H1 receptors on nerve endings and causes the ocular symptom of itching. Histamine also binds to H1 and H2 receptors of the conjunctival vasculature and causes vasodilatation. Mast cell-derived cytokines such as chemokine interleukin IL-8 are involved in recruitment of neutrophils. TH2 cytokines such as IL-5 recruit eosinophils and IL-4, IL-6, and IL-13, which promote increased sensitivity. Immediate symptoms are due to the molecular cascade. Encountering the allergen a patient is sensitive to leads to increased sensitization of the system and more powerful reactions. Advanced cases can progress to a state of chronic allergic inflammation. Diagnosis Classification SAC and PAC Both seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC) are two acute allergic conjunctival disorders. SAC is the most common ocular allergy. Symptoms of the aforementioned ocular diseases include itching and pink to reddish eye(s). These two eye conditions are mediated by mast cells. Nonspecific measures to ameliorate symptoms include cold compresses, eyewashes with tear substitutes, and avoidance of allergens. Treatment consists of antihistamine, mast cell stabilizers, dual mechanism anti-allergen agents, or topical antihistamines. Corticosteroids are another option, but, considering the side-effects of cataracts and increased intraocular pressure, corticosteroids are reserved