Microbiology of Lego

17 Jan 2017

Microbiology of Lego

Allison Cartwright is our ECS Publications Officer. Here, she looks at Lego and the microbes that may inhabit the world’s favourite brick.

“The sound a box of Lego makes is the noise of a child’s mind working, looking for the right piece. Shake it, and it’s almost creativity in aural form.” ― Grayson Perry, Playing to the Gallery

As soon as my dissertation was handed in, my mind moved back to a previous hobby – Lego. I boastfully bragged to my previous supervisor that I now have the time to build the Lego kits I’ve ignored during my project.

It wasn’t long before he pondered how the microbiology of my Lego would compare to those of a child. It’s a question that has foccussed my mind for the last few days.

Brick by brick

I excitedly dived into the world of published research with this question in mind, but I was disappointed to find a void, rather than a wealth of information.

Many of the suggestions focused on the role of toys in passing infection in paediatric wards in hospitals. While this is vital research, as sick children shouldn’t be exposed to further infection while playing, I wanted to focus on microbes on toys in everyday situations.

If I was still at uni, it wouldn’t have been a problem. I’d have made some agar, collected my Lego and some from a friend’s kid. My recent separation for uni meant I had to broaden the question or deduce the origins for microbes on the Lego.

Lip service

When observing small children with Lego, the bricks spend a lot of time near the mouth or being sat or stood on. Inevitably, my physical relationship with Lego is similar, but I don’t feel the need to chew them.

Wait a second … the best way to separate incorrectly placed bricks always involves my teeth. So, my Lego is probably coated in the same bacteria as a child’s, particularly those originating from my hands and saliva.

That’s handy

So, what microbes would I expect to find on my hands. A quick search delivered some common groups of bacteria including Pseudomonas, Staphylococcus and Acinetobacter. In addition, fungi and yeast could be found, including Aspergillus and Candida.

My Lego is likely to have similar microbial exposure as a child’s, but maybe the abundance would vary. I always wash my hands before building, but children often move from one toy to the next.

Washing will reduce, but not remove bacteria from my hands, so cleanliness would probably only reduce the amount of bacteria transfer, but wouldn’t stop it. Once I need to separate bricks, my mouth would definitely expose the Lego to microbes. This action will allow further exposure to Staphylococcus and Acinetobacter from the mouth or saliva, mine or a child’s.

Left on the shelf

So, if the bricks have similar exposure to microbes from an adult or child during building, it seems reasonable to expect they will have similar microbes. But what about the events once the model is complete?

This is probably the point when the microbes on the Lego start to diverge. When I finish my kit, after testing all the features, the model will be placed on a shelf, while a child will continue to play with it.

Ultimately, mine would be exposed to airborne microbes and a child’s will be exposed to human associated microbes and the microbial habitats explored during play. Think of a toy car, a child will test it on the carpet, tiled kitchen floor, street path and maybe even a bit of grass. In each of these play zones, different microbes have the opportunity to pass to the bricks and inevitably the child’s hands.

Toy story

During my search, one particular study caught my eye. The researchers, Martínez-Bastidas et al. (2014) had tested for bacteria and pathogens on children’s toys and hands from different  play zones. The toys used included dolls, bicycles and balls which were used on street paths or in parks.

Although the toys and children’s hands were washed before they played, Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae were found on both after playing on the streets or in parks. This indicates that my Lego may have less microbes than a child’s but only because I don’t move it to different habitats through play.

Dusty limits

The ability of microbes to pass from hand to toy and vice versa led me to think that microbes on toys are unavoidable, particularly when building Lego, or playing with the completed product.

However, I wonder if the microbes can settle and grow on the Lego or whether the microbes found are a reflection of the most recent play event?

My bricks also get occasional washes as it drives me (or my mother) mad if there’s dust or fingerprints on the shiny bricks.

Next time the dust on my Lego needs washing off, hopefully I’ll have some spare agar plates to test the bricks on. Then, after handling the Lego, I’ll see how much bacteria transfers and if they’re still detectable after the model has been sitting on a shelf once again.


Alli Cartwright

ECS Communications Officer


‘Everything is awesome, everything is cool when your part of a team/Everything is awesome, when you’re living out a dream’

Everything Is Awesome” – theme song to The Lego Movie


Martínez-Bastidas, T. et al., 2014. Detection of pathogenic micro-organisms on children’s hands and toys during play. Journal of Applied Microbiology, 116(6), 1668–1675

Microbe Wiki (2010) Human hands and fingernails [Online].  [Accessed 11 January 2018].

Rudney, J.D. (2000) Saliva and Dental Plague. Advances in Dental Research, 14(1), 29-39.