Grandma Was Right: Unwashed Ears and Toes Hide Skin Microbiome Secrets, Reveals Science

The age-old advice to scrub behind the ears and between the toes gets a scientific nod, with findings impacting the skin microbiome. 

A recent study from George Washington University dives into the skin’s microbiome. This unearths fascinating insights on how personal hygiene practices can sway skin health.

Harnessing Past Wisdom for Modern Science

Our grandmothers have long been the bearers of timeless wisdom, often emphasising the importance of thorough cleaning, especially behind the ears and between the toes. Turns out, they were onto something significant. A recent study led by a team at the George Washington University (GW) has brought to light intriguing connections between cleaning habits and skin microbiome health.

The skin, our body’s largest organ, is a bustling metropolis for a myriad of microbes known as the skin microbiome. These microscopic tenants play a crucial role in our overall health, influencing everything from skin conditions to immune responses. However, not all regions of our skin are created equal when it comes to microbial diversity. The researchers at GW sought to explore the microbiome of these often-neglected spots, coining their exploration as “the Grandmother Hypothesis.”

Scrubbing Unveils Microbial Mysteries

The innovative study, cheekily named after age-old cleaning advice, roped in 129 graduate and undergraduate students, teaching them to collect data by swabbing certain moist and oily hotspots – behind the ears, between the toes, and in the navel. For comparison, samples from drier areas like the calves and forearms, which are cleaned more thoroughly, were also collected.

Under the guidance of Marcos Pérez-Losada and Keith Crandall from the GW Computational Biology Institute, students embarked on a genomic journey, learning how to extract and sequence DNA from their skin samples. This hands-on approach allowed a deeper exploration into the microbial diversity in different skin regions.

A Tale of Two Microbiomes

The crux of the findings revealed that frequently cleaned areas like forearms and calves boasted a richer and potentially healthier collection of microbes compared to the lesser-washed hotspots. When troublesome microbes dominate, they can tip the scales away from health, leading to skin ailments such as eczema or acne.

This study not only endorsed grandma’s cleaning advice. It also highlighted how personal hygiene habits could significantly influence the microbial communities residing on our skin, thus impacting its health status.

Researchers collected skin swabs from the belly button, behind both ears, between the toes of both feet, both calves, and both forearms. These regions were chosen because they represent distinct microenvironments, including oily, moist, and dry areas of the skin.

Key Findings

1. Taxonomic Diversity

  • The researchers used advanced sequencing techniques to characterise the skin microbiome. They found that the skin bacteriome was primarily composed of four dominant bacterial phyla: Actinobacteriota, Bacteroidota, Firmicutes, and Proteobacteria.
  • The most abundant bacterial genera detected across all samples included Staphylococcus, Corynebacterium, Anaerococcus, Escherichia-Shigella, Prevotella, Streptococcus, Peptoniphilus, Porphyromonas, and Finegoldia.
  • Interestingly, only two specific bacterial genera, Staphylococcus and Corynebacterium, were consistently present in all samples. This suggests that these bacteria may represent the core members of the skin microbiome.

2. Spatial Variation

  • The study revealed significant variation in both taxonomic and functional diversity across different skin regions and microenvironments.
  • Dry skin regions, such as the calves and forearms, exhibited the highest diversity of bacterial communities. Moist regions showed lower diversity.
  • Sebaceous (oily) areas, like behind the ears, had a unique bacterial composition dominated by Firmicutes.

3. Functional Diversity

  • In addition to taxonomic diversity, the researchers investigated the functional diversity of the skin microbiome using computational tools.
  • They identified a wide range of metabolic pathways that were differentially expressed across skin regions and microenvironments. This highlights the functional versatility of the skin bacteriome.


This comprehensive study offers a glimpse into the intricate world of the skin microbiome. It highlights the importance of understanding how spatial variation, micro-environmental factors, and skin regions influence the composition and function of the skin bacteriome. These findings provide a valuable reference for future research, including studies focused on skin diseases and the impact of internal and external factors on the skin microbiome.

In the quest to unlock the mysteries of the skin microbiome, this study represents a significant step forward. As we continue to explore the role of these communities in skin health and disease, we may uncover new avenues for therapeutic interventions and personalised skincare routines.

Pioneering Insights for Future Research

This study is one of the first of its kind. It lays a solid foundation for future research in understanding how the collection of microbes on the skin can lead to health or disease.

The team’s findings opens new avenues for research aiming at promoting skin health and preventing skin diseases.

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