Neurotrophic factors and nerve growth factor in ocular allergy Purpose of review During allergic reaction, nervous and immune systems mutually interact through release of mediators, including neurotrophic factors and nerve growth factor (NGF). These mediators modulate allergic reaction through binding their receptors expressed by immune and structural cells and by stimulating neuropeptide release by nerves. The role of neuropeptides and NGF has been demonstrated in allergic asthma and rhinitis, and, to a lesser extent, in allergic conjunctivitis. The aim of this review are to elucidate the evidence of the role of NGF and neuropeptides in the pathogenesis of allergic conjunctivitis. Recent findings NGF modulates allergic reaction by stimulating release of cytokines, inflammatory mediators and neuropeptides by immune and structural cells and nerve endings at the site of inflammation. Evidence showed that local and systemic NGF levels increase in patients with allergic conjunctivitis, including allergic rhinoconjuncivitis, vernal keratoconjunctivitis and atopic keratoconjunctivitis. We recently described an increase of conjunctival p75NTR expression in patients with allergic rhinoconjuncivitis, and an increase of tear levels of NGF after conjunctival provocation test with allergen. Summary NGF modulates ocular allergic reaction. Increasing understanding of the role of neuropeptides in allergic conjunctivitis may pave the way to the development of novel therapeutic approaches and improvement of patients’ management. Correspondence to Professor Alessandro Lambiase, Department of Sense Organs, University Sapienza of Rome, Vilae del Policlinico, 155, 00161 Rome, Italy. Tel: +39 064 997 5357; e-mail: alessandro.lambiase@uniroma1.it Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.