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Bathing might seem like second nature—something we've always instinctively known how to do properly. However, as we discovered during the viral 2019 debate about whether it's essential to wash your legs in the shower, not everyone follows the same showering routine. While we're all taught to wash our hands, many of us also grew up with reminders from family to clean behind our ears, between our toes, and inside our belly button when showering or bathing.
Intrigued by the influence of old-fashioned hygiene advice, researchers at George Washington University (GW) decided to test what they call the 'Grandmother Hypothesis.' Here are the key findings from the study, alongside dermatologist and family medicine expert advice on how to properly clean these three frequently ignored areas in the shower.
Skynesher/Getty ImagesWhat is the Grandmother Hypothesis?
Keith Crandall, PhD, a professor of biostatistics and bioinformatics at GW, recalls that as a child, his grandmother would tell the children in the family to 'scrub behind the ears, between the toes, and in the belly button.' These early instructions form the foundation of what Crandall and the research team at the GW Computational Biology Institute now call the 'Grandmother Hypothesis.' This theory suggests that people tend to neglect cleaning these specific body parts as thoroughly as others, like their arms and legs, which may cause harmful bacteria to build up, potentially harming a person's health.
The Study's Findings: Does the Grandmother Hypothesis Hold Up?
Researchers examined skin samples from 129 graduate and undergraduate students and found that microbes from body areas commonly washed, such as forearms and calves, exhibited greater diversity. This diversity is associated with a potentially healthier microbiome compared to areas such as behind the ears, between the toes, and inside the belly button, which showed less microbial variety.
In a study published in the September edition of the journal Frontiers in Microbiology, Crandall and colleagues explain that if moist, oily body areas like the ears, toes, and belly button aren’t washed frequently enough, harmful microbes can disrupt the skin’s microbiome. This imbalance may lead to skin issues like eczema or acne. However, the authors also point out that due to the limited sample size and the few areas swabbed, further studies are needed to get a clearer understanding of how our washing habits affect our health.
Laura Purdy, MD, a family medicine physician from Miami who was not involved in the GW study, emphasizes that this research highlights the importance of thoroughly cleaning every part of our skin during bath time—particularly those often overlooked or difficult-to-reach areas like behind the ears, between the toes, and inside the belly button.
Dr. Purdy further explains, 'Washing our body not only eliminates dirt, odor, and allergens accumulated throughout the day, but it also removes dead skin cells, sweat, and the natural oils present on our skin. Our skin can harbor bacteria, viruses, or fungi, making it crucial to cleanse these areas for optimal skin health.'
Now, let’s dive deeper into each of these three body areas to understand the consequences of neglecting them during cleaning, and learn the best practices for proper care.
Behind the Ears
In areas with skin folds or creases, like behind the ears, body oils (sebum), shedding skin cells, and dirt can accumulate, leading to skin irritation. According to Stacey Tull, MD, a double-board-certified dermatologist and micrographic dermatologic surgeon from Cottleville, Missouri, this buildup may cause seborrheic dermatitis—a skin condition akin to dandruff found on the scalp.
According to Dr. Purdy, seborrheic dermatitis can result in the appearance of white or yellow flakes on the scalp, including the area behind your ears. These inflamed regions may begin to itch and flake. Dr. Tull points out that any skin inflammation can create cracks in the skin barrier, making it easier for bacteria to enter and potentially cause infections.
Dr. Purdy also warns that neglecting to wash behind your ears may lead to the skin becoming sensitive or irritated. Over time, this can result in eczema. For those with pierced ears, she stresses the importance of regularly cleaning this area to avoid infection.
Odor can also become a concern. Dr. Purdy explains, 'There are sweat glands behind your ears, so sweat is naturally produced. When sweat interacts with bacteria, it can begin to emit an unpleasant smell over time.'
No special technique or product is required to wash behind your ears; the most important factor is consistency. Dr. Tull emphasizes, 'Cleaning behind your ears should be no different than washing the rest of your body.'
Dr. Purdy advises using the same soap you typically use, and if you use a washcloth for other areas, feel free to use it behind your ears as well. She personally prefers using soap and the friction of her fingers to wash both her face and body. Dr. Purdy concurs, stating that gently rubbing with your fingertips behind the ears is all that’s needed.
Between the Toes
Although water and soap from your shower may wash over your feet and toes, it doesn’t do a thorough job of cleaning the spaces between them.
Dr. Tull explains that the skin between the toes doesn’t produce as much oil as other areas, which means that neglecting to wash here leads to a different kind of buildup—primarily dead skin cells and dirt. She also warns that this could potentially lead to nail fungus.
Dr. Purdy adds that our feet sweat excessively, and because shoes trap that moisture, bacteria and fungus can thrive. 'This can lead to athlete's foot, a fungal infection typically found between the toes,' she explains. 'Symptoms include itching, peeling, scaling, and the development of rashes or cracks on the skin.'
Neglecting to wash between your toes can also result in bacterial dermatitis or cellulitis, a skin infection that may spread up the leg, according to Dr. Tull. She stresses the importance for diabetics to keep their feet and toe spaces clean, as they are more susceptible to skin infections.
Cleaning between your toes is simple and should be part of your regular shower routine, ideally every one to two days, according to Dr. Tull. For those who can’t take a full shower as frequently, a foot bath is an effective alternative. 'You can use the same products you'd normally use to wash your body for cleaning your feet,' she adds.
Dr. Purdy suggests using soap to wash your feet, including the areas between your toes, and ensuring they are rinsed thoroughly. 'Don’t forget to change your socks regularly,' she emphasizes. 'Socks collect bacteria and buildup, so it’s crucial to wash them between wears.'
Inside the Belly Button
Both doctors stress the importance of cleaning your belly button, whether you call it a 'navel' or 'belly button.' Dr. Purdy points out that this area is dark, moist, and has multiple skin folds, making it a perfect environment for the buildup of dead skin cells, sweat, and microorganisms like bacteria and fungi.
This neglect can lead to unpleasant odors, and the friction from skin rubbing together can make the area vulnerable to infections, such as staph or yeast infections. Dr. Purdy explains that the area may become irritated, inflamed, red, itchy, and even develop scabs or a yellow crust.
Dr. Tull suggests cleaning your belly button every one to two days, noting that no special soap is needed, just like other areas we’ve discussed. However, for those with sensitive skin or conditions like eczema, Dr. Purdy recommends using a soap or body wash that suits your skin type. She also emphasizes that individuals with a navel piercing 'should definitely make sure to care for and regularly wash this area.'
To clean your belly button, all you need is a soapy finger to gently rub the inside and then rinse. While some people prefer using a cotton swab, Dr. Tull advises being gentle with any tool, stressing that 'care must be taken not to be too harsh, like digging with a Q-tip, as this could cause additional trauma.'
