present with a red, painful, watery eye The conjunctival injection is usually sectoral Presence of concomitant vesicular lesions in the eyelid region helps raise concern for HSV infection, however skin lesions need not be present Patients with herpes zoster ophthalmicus experience pain, often followed by development of vesicular lesions in the involved dermatome (i.e., ophthalmic division of trigeminal nerve), which is commonly associated with significant lid swelling and pain ( Fig 123.9 ) Corneal involvement may occur to days after skin lesions are seen Airborne or contact allergic conjunctivitis is characterized by hyperacute conjunctival injection associated with watery tearing and a blister-like swelling of the conjunctiva (chemosis) ( Fig 123.10 ) Itching is often a prominent symptom The history may reveal recent exposure to an environmental allergen (e.g., cat dander) Seasonal allergic conjunctivitis, a recurrent reaction to outdoor pollens, typically has a less dramatic onset Patients may have a history of atopy such as allergic rhinitis, asthma, or eczema TABLE 123.1 DIFFERENTIAL DIAGNOSIS OF CONJUNCTIVITIS