Grandma, you were right: science has confirmed the ancient theory about washing different areas of the body.

A team of researchers from the Institute of Computational Biology at George Washington University has investigated the “grandma hypothesis” regarding washing different areas of the body and found that people often overlook several key spots, such as the navel and the area behind the ears. This neglect can harm the health of the skin’s , which is the community of microorganisms living on the skin.
Kit Crandall, the institute’s director and a professor of biostatistics and bioinformatics, shared in 2023 that his grandmother always told him to “scrub behind the ears, between the toes, and around the navel.” He speculated that these areas might harbor bacteria due to inadequate washing, differing from those found on other parts of the body.

During the study, samples of skin were collected from the calves, forearms, behind the ears, between the toes, and around the navel from 129 students. These students were trained to sequence from these samples, comparing data from oily, unwashed skin areas to drier, cleaner ones.
It turned out that both Grandma Crandall and her professor grandson were right: in the areas that students washed more thoroughly, the microbiome was significantly more diverse and contained a potentially healthier collection of microbes than in the neglected zones.
“The dry skin on the forearms and calves is smoother, richer, and functionally different from the oily (behind the ears) and moist (navel and between the toes) areas,” the researchers wrote in their report.
Interestingly, this pattern held true regardless of the participants’ gender, age, or ethnicity, as reported by IFLScience.
consists of both beneficial and harmful microbes. When the balance shifts toward harmful ones, it can lead to conditions such as eczema or acne, noted Professor Crandall.
According to the researchers, the relationship between microbiome health and human health still requires serious investigation.
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