Scientists offer first glimpse of bacteria living in ear piercings

Human skin piercings create hospitable homes for a diversity of bacteria.

A study by Canadian scientists offers the “first glimpse into the bacterial communities inhabiting human ear-piercings”, publishing their findings in the Proceedings of the Royal Society.

“Skin piercing has been practiced as a form of cultural, religious, and personal expression in human societies for thousands of years; our study reveals that it also represents a form of ecosystem self-engineering of the ecological landscape that is the human skin,” the authors write.

Researchers from McGill University recruited 28 individuals about to receive an ear piercing at Tattoo Lounge in Montreal in 2019 and 2020.

The participants’ earlobes were sterilised, and skin swabs taken from the earlobe before and after piercing. Participants then collected swabs – of their ear, as well as the air as an environmental control – at 12 hours, 1 day, 3 days, 1 and 2 weeks following the piercing.

Piercing microbiome royal soc b image 1
Credit: Charles C.Y. Xu licensed under CC BY-SA 4.0

DNA analysis of the samples revealed a significant increase in the diversity of bacteria at the piercing site, while bacteria remained stable in unpierced areas.

“Skin piercings likely represent the creation of hospitable niches for certain bacteria,” the paper says. “[They] thrive in areas of greater occlusion, moisture, and nutrient retention”. The study adds: “piercing studs may physically trap and accumulate debris including sweat, sebum and pieces of stratum corneum that serve as primary nutrient sources for most human skin microbiome members.”

No relationships were identified between the diversity of bacteria and participant behaviours such as hygiene, travel or physical activity.

Two species – Cutibacterium acnes and Staphylococcus epidermidis – known “opportunistic pathogens of human skin” encompassed more than half of the bacterial community in the piercing site. While an excess of either species can create problems, S. epidermidis is the most common source of infections on indwelling medical devices such as central venous catheters and joint prostheses.

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