Allergic conjunctivitis is an increasingly prevalent allergic disease, with the same clinical gravity as allergic asthma and allergic rhinitis. • The umbrella term “allergic conjunctivitis” includes distinct clinical entities, from mild but disturbing forms due to IgE sensitization to aeroallergens, to forms of keratoconjunctivitis where the severe allergic inflammation, with corneal involvement, is more difficult to diagnose and treat, and may lead to permanent ocular damage and even loss of vision. Introduction Allergic conjunctivitis is the most common cause of a red eye, affecting more than one billion people globally. There are several clinical forms of allergic conjunctivitis; intermittent or seasonal (SAC), persistent or perennial (PAC), vernal (VKC), atopic (AKC) and induced by contact lenses (CLC). Symptoms and Severity Although some symptoms are similar in all forms (itching – which is typical of allergic conjunctivitis, distinguishing it from other forms of a red eye – redness, tearing and photophobia), the pathophysiology, disease associations, and clinical presentation can differ, for example, the giant papillae in VKC and CLC. The disease severity and management are different in these phenotypes of ocular allergy (Figure 2). While SAC and PAC (very often associated with rhinitis) impair a patient’s quality of life they are mild diseases and are easily controlled by adequate anti-allergic treatment. On the other hand, VKC (occurring alone or more frequently associated with asthma, particularly in young boys before puberty and in some geographical regions with intense natural light) and AKC (typically associated with atopic eczema) are rare but severe clinical entities, in which the involvement of the cornea (vernal and atopic keratoconjunctivitis) is difficult to treat and may eventually cause impairment of visual function. WAO White Book on Allergy 3 1 Copyright 2011 World Allergy Organization A C B D Figure 2. Seasonal Allergic Conjunctivitis (A) vs Vernal Keratoconjunctivitis (B,C,D). Note the corneal involvement (B) and the giant papillae at tarsal (C) and limbar (D) level. The allergist has a central role in the diagnosis of allergic conjunctivitis. Patients with bilateral red itching eyes should always be referred to the allergist not only for skin testing and IgE determination, which may be negative, particularly in some cases of VKC and AKC, but also to evaluate general and ocular clinical symptoms. The allergist can also arrange for more sophisticated tests such as the detection of eosinophils in tears, which is typical of VKC and AKC, or of SAC and PAC during the acute phase. The age of the subject, the clinical association with asthma or eczema, the presence of ocular pain or of an intense photophobia, and a poor response to common anti-allergic treatments should prompt the allergist to consult an ophthalmologist to evaluate the presence of a possible corneal involvement. Therapeutic Considerations An adequate treatment of rhinitis with topical steroids, immunotherapy when indicated, systemic and topical antihistamines (or more recent molecules with a dual antihistaminic and anti-inflammatory action) may easily control SAC and PAC. The corneal involvement in VKC and AKC often requires the use of steroids, with the potential for severe iatrogenic side effects of these drugs in the eye (glaucoma, ulcers). Future Research Needs Research efforts in allergic conjunctivitis should mainly be devoted to the most severe forms of ocular allergy (SOA), in an attempt to clarify their pathophysiology better, to standardize diagnosis, and to suggest new forms of treatment. Recommended Reading 1. Bielory L, Bonini Se, Bonini St. Allergic eye disorders. In: Inflammatory mechanisms in allergic disease. B. Zweiman, LB Schwartz Eds. Marcel Dekker, New York 2002, 311-323. 2. Bonini St, Sgrulletta R, Coassin M, Bonini Se. Allergic conjunctivitis: update on its pathophysiology and perspectives for future treatment. In: R. Pawankar et al Eds. Allergy Frontiers: Classification and Pathomechanisms. Springer, Basel 2009, 25-48. 3. Ono SJ, Abelson MB. Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol 2005; 115:118-122. 2.1.3 Rhinosinusitis Key Statements • Rhinosinusitis (RS) is one