Allergy and Dry Eye Disease.

Ocular allergy (OA) and dry eye disease (DED) are the most common ocular surface disorders with a potential severe impact on the patient's quality of life. OA and DED may coexist and have a significant clinical overlap. Therefore, clinical features commonly believed to be distinctive of OA or DED may be sometimes insufficient for a differential diagnosis. Alterations of the tear film, epithelial barrier, and corneal innervation are described in OA and can pave the way to DED. Conversely, DED may facilitate or worsen allergic reactions in predisposed (atopic) patients. For these reasons, OA and DED should be considered as reciprocal predisposing conditions that share ocular surface inflammation as a common background.