If you’ve ever wondered which office items carry the most dirt and bacteria, spare a suspicious glance at the large flat surface directly beneath your elbows.
An office hygiene experiment commissioned by digital workplace specialist DTP Group found the desk carried the highest bacterial load of the surfaces tested — registering 4.5 times more bacteria than the computer mouse.
Strictly speaking, the experiment measured bacteria rather than dirt, but the distinction is unlikely to make your lunchtime sandwich feel much happier.
Office kitchens get wiped. Bathrooms are cleaned with reassuring regularity. Desks, meanwhile, spend their days collecting hands, coffee cups, phones, crumbs, laptops and the occasional lunch eaten over an Excel spreadsheet. Then everyone goes home and assumes somebody else has dealt with it.
Apparently, somebody often hasn’t.
The desk was the bacterial heavyweight
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DTP Group tested frequently used office items including the desk, keyboard, laptop, screen, mouse and chair.
The desk produced the highest bacterial load, while the chair ranked second. Keyboards and laptops also returned comparatively high counts, which will surprise nobody who has ever turned a keyboard upside down and discovered enough organic matter to constitute a small packed lunch.
The mouse fared considerably better. According to the results, the desk contained 4.5 times its bacterial load.
There is an obvious behavioural explanation. A mouse generally meets one hand. A desk gets everything.
Why keyboards, desks and laptops collect bacteria
DTP Group worked with Dr Primrose Freestone, Associate Professor in Clinical Microbiology at the University of Leicester, whose academic expertise in microbiology and public engagement is confirmed by the university.
Freestone explains that the results largely reflect ordinary human contact: “Well, the bacterial counts of desk, keyboard, and laptop were the highest of the swabs and are not surprising as they involve hand contact, and hands, palms and fingers are known to be very well colonised by both their endogenous microbiome and whatever the hands encounter.
It is what we pick up microbiologically that explains why we need to wash our hands so often. The screen has fewer microbes as it is touched less, and the mouse is used by only one hand, so again this explains the fewer counts.
Now the chair has a higher count as it reflects the higher numbers of bacteria resident on your bottom and underwear that have moved through your clothing onto the chair cover.
Your bottom area will also release sweat which feeds the bottom and underwear bacteria and also explains why we get BO.
All in all, the swabs show something that is both dynamic and reflective of what is always happening wherever a human goes, that is, we leave a fingerprint of our microbiomes on whatever we touch, sit on or wherever we eat.
The swab counts are not massively high because of how the swabs were cultured and also because it is likely that only one or a few people may have occupied the desk and chair, and microbes on their surfaces will inevitably die over time.
Plus if the desk is wooden, the wooden fibres themselves can be antimicrobial, as can any polish on the desk or chair.”
The chair explanation may not improve office morale, but microbiologically it makes perfect sense.
A dirty surface isn’t automatically a dangerous one
There is a useful distinction here. Finding bacteria does not automatically establish that a surface is hazardous or likely to make somebody ill.
Human skin naturally carries a substantial and diverse microbial population. Some organisms are resident members of the skin microbiome; others are picked up temporarily from surfaces and people around us.
That makes bacterial counts interesting evidence of how heavily surfaces are used, but they should not be confused with a direct measurement of infection risk.
There is another limitation. The study summary does not provide a detailed sample size, identification of individual bacterial species or a peer-reviewed methodology. Its league table is therefore better regarded as an illustrative snapshot of office hygiene than a universal ranking for every workplace in Britain.
Your desk is grubby. It has not yet applied for biological weapons status.
Five ways to clean the dirtiest office items
The practical advice is reassuringly mundane.
Clean the whole desk regularly. Pay attention to areas beneath equipment and around the places where hands, food and drinks routinely land, rather than performing the traditional ceremonial wipe of the only bit already visible.
Give the keyboard and mouse some attention. Debris can be removed from between keys before appropriate cleaning wipes are used on contact surfaces. Shared equipment deserves more frequent cleaning between users. Wash your hands properly. This remains more important than developing an unhealthy emotional attachment to disinfectant.
The NHS recommends washing with soap and water for around 20 seconds, particularly before eating and after activities likely to contaminate the hands.
Consider eating somewhere else. Crumbs and moisture deposited around a workstation provide additional material for microorganisms, quite apart from the psychological benefit of spending lunch somewhere that does not contain your inbox.
Don’t forget the chair. Armrests and seat backs receive frequent contact yet rarely feature prominently in office cleaning routines. Hot-desking makes that omission particularly difficult to defend.
The office hygiene habit that matters most
The larger lesson isn’t that workers need to spend their afternoons stalking bacteria with a packet of wipes.
It’s that offices are ecosystems of constant contact. Hands touch phones, keyboards, doors, mugs, desks and faces, then cheerfully begin the circuit again. Public-health guidance continues to identify proper handwashing as one of the simplest ways to reduce the transfer of germs between people and surfaces.
Cleaning frequently touched equipment is sensible. Eating lunch away from the keyboard is even more sensible. Washing your hands before returning to the sandwich may be the best investment of all.
And perhaps give the desk a wipe occasionally. It has apparently been getting away with murder while everyone blamed the mouse.
