At the beginning of this year, I was contacted by the University press office regarding a request from a BBC Morning Live producer to examine personal care products for bacterial presence. Following conversations about the proposed study, our lab conducted initial tests on toothbrushes, uncovering the presence of bacteria, including coliforms indicating fecal contamination. A few more meetings with the producers led to expanding the research to include hairbrushes and makeup brushes, which also revealed some interesting results.
One out of every four toothbrushes harbors fecal bacteria, as do five out of every six hairbrushes
Once we had gathered all samples, Panward conducted the analysis, which consisted in either scrubbing the makeup brushes and hairbrushes with sterile cotton buds then streaking out on agar plates, or soaking the toothbrushes in sterile water and then streaking out on agar plates. Our research revealed that 26% of the toothbrushes we examined contained faecal bacteria, while 11% harbored other types of bacteria. Interestingly, we did not observe a link between the distance of toothbrush storage from the toilet and the presence of faecal bacteria. This suggests that water splashes and aerosols from the toilet are not necessarily accountable for transferring faecal bacteria to toothbrushes. Additionally, the age of the toothbrush did not influence the presence of bacteria on it. In contrast, when we investigated a dozen makeup brushes, we did not detect any bacteria, which contrasts with findings from similar studies that reported high levels of bacteria on used makeup brushes, sometimes surpassing those found on a toilet seat. When examining hairbrushes, we discovered that 83% of them contained faecal bacteria, and 67% harbored other types of bacteria. It is plausible that these bacteria reside on our hair and could be picked up while traveling on public transport or visiting places like hospitals, known for their high bacterial presence. Notably, public transport seats, such as those on the the London tube, are known to be teeming with bacteria like Escherichia coli and Pseudomonas aeruginosa, which can lead to pneumonia and meningitis.
What are the consequences of discovering bacteria on toothbrushes and hairbrushes?
Bacteria are found everywhere, including within our bodies on our skin, hair, and in our mouths. The oral microbiome is particularly diverse, containing over 500 species of bacteria (such as Streptococcus and Corynebacterium), fungi (such as Candida and Malassezia), and viruses (such as bacteriophages) [1, 2]. Generally, fecal bacteria like E. coli can lead to diarrhea if consumed, while other bacteria can contribute to issues like plaque (mainly caused by Streptococcus mutans), gum disease, mouth sores, and halitosis.
Similarly, the hair follicle microbiome harbors a diverse microbial community distinct from that on the rest of the skin. It has been observed to undergo changes in its composition under specific pathological conditions like dandruff and alopecia [3]. Although there is no evident connection between the presence of E. coli or other fecal bacteria on the scalp and diseases, individuals with dandruff exhibit a higher prevalence of the yeast Malassezia restricta and Staphylococcus spp. bacteria compared to the general healthy population [4].
Hairbrushes tested and the resulting bacteria that could be cultured from them.
Take-home messages
Our body is home to bacteria and yeasts, which can be found on our skin, hair, and in our mouth. While having them on our toothbrush or hairbrush is usually not a cause for concern, maintaining good hygiene is always beneficial. It is advisable to clean hairbrushes and makeup brushes every 7-10 days using lukewarm water and shampoo, and to replace toothbrushes every three months, primarily due to the bristles deteriorating and becoming less effective in cleaning our teeth.
Links
The results of the study on toothbrushes were discussed in the 25/10/2024 episode of BBC Morning Live: https://www.bbc.co.uk/programmes/m002470m. You can also see the specific clip here: https://www.bbc.co.uk/programmes/p0k04pkr.
The results of the study on hair brushes were presented in the 30/10/2024 episode of BBC Morning Live: https://www.bbc.co.uk/programmes/m0024g89. The clip is available here: https://www.bbc.co.uk/programmes/p0k173gj.
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