Spontaneous face- and eye-touching: Infection risk versus potential microbiome gain

Abstract

The COVID-19 pandemic has compelled a review of possible routes of microbial infection, of particular importance since the ocular surface is a likely portal of human Coronavirus invasion. As hand contamination is considered an important and potentially preventable factor for transmission, we have reviewed face touching in the context of a group of disorders known as the Body-Focused Repetitive Behaviours (BFRPs). Spontaneous face-touching is a poorly understood, atavistic, ingrained habit for humans, who engage in this activity approximately 26 times per hour. Nearly half of spontaneous face-touches involve mucous membranes, and one third of those involve the eyes. Historically the majority of research of this curious phenomenon has focused on psychological aspects, despite its pertinence to a range of anterior eye diseases such as keratoconus, trichotillomania and mucus-fishing syndrome. The ocular infectious sequelae through chiral auto-inoculation are well known for diseases including the conjunctivitides, herpetic keratitis, and papillomatosis. Furthermore, touches to the ocular mucous membranes also play an important role in systemic disease through access to the respiratory and gastrointestinal tracts via the nasolacrimal duct and nasopharynx, and may be relevant to SARS-CoV-2 infection. Through this access, chiral touches may also play a significant role in building and maintaining the microbiome, which has been increasingly implicated in ocular disease. This article reviews spontaneous self-touches, and their significant ramifications for ocular and systemic health and disease.