Allergic rhinoconjunctivitis and differential diagnosis of the red eye

Red eye is a common presentation in clinical practice with conjunctivitis being the most common cause of red eye. Most commonly, conjunctivitis is infective (bacterial and viral) or allergic in origin although other forms of conjunctivitis including toxic and irritative conjunctivitis and conjunctivitis related to systemic conditions or dry eye are prevalent enough to warrant consideration in diagnosis. This article aims to provide a guide for generalists and allergists in the differential diagnosis of conjunctivitis allowing the inclusion of eye treatment into their current practice. With a discussion of important aspects to include in the patient history as well as a systematic guide to examination of the eye for generalists and allergists, this article provides a "plan of action" in the examination protocol for red eye patients. A differential diagnosis table and flowchart are provided as a useful chair-side reference for practitioners. With a particular focus on the more prevalent types of conjunctivitis, typical features, signs, and symptoms of each type are detailed. A general discussion of prognosis and treatment options and conditions that require ophthalmologic referral is included.