key: cord-0774936-wbj9tq7h
authors: Spencer, Sascha K.R.; Francis, Ian C.; Coroneo, Minas T.
title: Spontaneous face- and eye-touching: Infection risk versus potential microbiome gain
date: 2021-04-30
journal: Ocul Surf
DOI: 10.1016/j.jtos.2021.04.008
sha: 116f0cea0c11461c8de25352cd355f4898d8adbe
doc_id: 774936
cord_uid: wbj9tq7h

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.

Authors 1 Spencer et al. Face and eye touching Spontaneous self-touches are the contact movements of the body and face by the hands and fingers, not associated with deliberate decision-making processes 1, 2 .

Despite decades of research, they remain a poorly understood phenomenon, although in the last year they have piqued interest for their role in the spread of SARS-CoV-2 3 . In the discussion surrounding improving infectious risk through reducing spontaneous face-touches (SFT), one question does not seem to have been asked: Why do we touch our face so often to begin with?

The infectious risk of SFT is not limited to COVID-19. SFT have been attributed to many diseases, as is well-documented in ophthalmology. Infectious conjunctivitis, the most common ocular infection, is believed to be spread most often through handeye touch following contaminated source exposure. Other pathogens, spread through SFT, such as the herpes simplex virus (HSV) and human papillomavirus In the literature there are reported associations of SFT with underlying negative affect, anxiety, or discomfort, and they may serve to comfort and release emotional arousal 2 . They may also represent an attempt to shield the self from distraction, with associations to working memory and emotions 1,2 . In a literal sense, they increase 'brain power'. In one study of self-touching utilising electroencephalography (EEG), spontaneous self-touches changed the theta frequency above the parietal and occipital lobes, and increased the theta and beta power 2 . These EEG changes were only seen when self-touch was spontaneous; instructed touches did not have the same effect 2 .

J o u r n a l P r e -p r o o f However, there may be a further significant benefit to SFT. The hands harbour greater bacterial diversity and have greater temporal variability in their composition than any other body site 7 . While SFT has previously been hypothesised as the cause of colonisation of healthcare workers with S aureus 1 , we hypothesise that SFT may be important, or perhaps even essential, in developing and maintaining the diversity of the human microbiome. SFT brings the hands, the part of the body the most physically in contact with the external world and with the highest temporal microbial diversity 7 , to the areas of the face where these microbes may access the mucous membranes, and the gastrointestinal and respiratory systems beyond.

Diversity is integral in maintaining microbiota homeostasis, with self-touch potentially serving as a pathway to increasing diversity in the microbiome of the ocular surface, skin, gastrointestinal and respiratory tracts, as supported by the high percentage of touches involving mucous membranes.

If true, this would denote a significant impact of SFT on ocular, and even systemic, health and disease. Microbial symbiosis has been implicated not only in infectious disease, but also immunological, endocrinological and neurodegenerative diseases, including those that affect the eye 8 . Commensal and mutualistic microbiota, including those of the ocular surface, protect against foreign and opportunistic pathogenicity through competitive exclusion and antimicrobial substance production, and influence innate immunity 8 . Microbiome dysbiosis may occur through loss of beneficial organisms, excessive growth of potentially harmful organisms, or loss of overall microbial diversity. Dysbiosis leading to epigenetic reprogramming and inflammation has been implicated in autoimmune uveitis, age-related macular degeneration, and recently even open angle glaucoma 8 .

Diversity of microbiota is paramount. In mouse models of Sjogren's syndrome, desiccating stress and antibiotics significantly increased dry eye phenotype, with severity inversely correlated to microbial diversity 8 

Pseudomonas aeruginosa-induced keratitis became susceptible when raised germfree, with the ocular microbiome by itself having a significant impact on resistance 8 . Perhaps the commensal microbial immunity benefit of SFT has, from an evolutionary perspective, balanced against its significant infective risk 9 .

While the hypothesised effect on the microbiome represents a potential significant benefit of SFT on ocular and systemic health, in the current pandemic climate the potential risk of systemic disease through the ocular surface seems to have been largely ignored. Currently many cities and countries around the world are recommending or enforcing by law the wearing of face masks in public. However, the ocular surface and periorbital landing area unshielded by face masks, represents an absorptive area of up to ~10,000 mm 2 6 .

By means of a reduction in SFT, however, the protective benefits of wearing a mask may extend beyond barrier defence of the nasopharynx and oropharynx. Wearing a face mask is significantly associated with a decreased rate of SFT; in health professionals, SFT decreased, by an average of 20 times per hour without a mask, down to 5.4 times with one 10 . However, in studies to date the number of touches to the ocular surface was not reported, nor were the numbers of mask-touches. While this reduction in SFT is encouraging, it is important to note that with face masks alone, the ocular surface still remains at risk.

Touching behaviours are more complex than is usually appreciated in ophthalmological practice, yet they may play an unexpected role in both ocular and systemic health and disease 9 . Whilst SFT may be important in mutualistic microbiota exposure, this also increases the risk of pathogen exposure. In high risk states such as during an infective pandemic, it becomes crucial to be able to take steps to defend against pathogenicity through auto-inoculation. While the principal mode of transmission for SARS-CoV-2 appears to be via droplet spread, contamination of the hands followed by inoculation of the mucous membranes could potentially provide alternative mechanisms of viral transmission. The challenge from a personal as well as population perspective is for everyone's protection to be improved and made more effective.

J o u r n a l P r e -p r o o f

Face touching: a frequent habit that has implications for hand hygiene

EEG changes caused by spontaneous facial self-touch may represent emotion regulating processes and working memory maintenance

How Frequently Do We Touch Facial T-Zone: A Systematic Review

Treatment of previously refractory ocular surface squamous neoplasia with topical cidofovir

Handwashing and risk of respiratory infections: a quantitative systematic review

The eye as the discrete but defensible portal of coronavirus infection

Review of human hand microbiome research

Visions of Eye Commensals: The Known and the Unknown About How the Microbiome Affects Eye Disease

Spontaneous eye-and face-touching: A balance of benefit and risk in ocular and systemic health and disease