Beauty products may harm your skin's natural disease fighters

Recent research suggests that everyday items like antibacterial soap, houseplants, and makeup could influence human health by altering the skin microbiome, potentially affecting susceptibility to chronic diseases. While scientists continue studying what constitutes a healthy skin microbiome, mounting evidence indicates its crucial role in disease prevention and immune system regulation.

The skin hosts millions of microorganisms - bacteria, viruses, and fungi - that work together to maintain human health. José C. Clemente, associate professor of genetics and genomic sciences at Icahn Mount Sinai, emphasizes the skin microbiome's defensive role. "We think that skin microbes are important because the skin has always been our first barrier of defense against the environment," said Clemente.

While researchers have extensively studied the gut microbiome, which contains the body's largest concentration of microbes, some experts believe the skin microbiome's importance has been underestimated. Daily environmental exposures can alter the microbial composition on the skin, potentially disrupting the balance between beneficial and harmful microorganisms.

Julia Oh, microbiome researcher and dermatology professor at Duke University, points out the broader implications of an imbalanced skin microbiome. "Multiple systemic inflammatory diseases have been identified to have links to an imbalanced skin microbiome," Oh said. These conditions extend beyond skin-specific issues like psoriasis and eczema to include asthma, tooth decay, inflammatory bowel disease, and certain types of arthritis.

The skin microbiome serves multiple protective functions. According to Julie Segre, geneticist at the National Human Genome Research Institute, these microorganisms break down skin oils, maintain barrier function, and produce substances that combat bacteria and inflammation. Perhaps most importantly, they educate the immune system about which organisms to tolerate and which to fight.

The skin contains between three and four percent of the body's immune cells. Segre explains that exposure to various natural skin microbes teaches the immune system to tolerate beneficial or harmless organisms. Without this education, the immune system may become hyperactive, increasing the risk of allergies and autoimmune conditions where the body attacks itself.

Research indicates that greater microbiome diversity correlates with lower disease risk. One study of an isolated Yanomami Amerindian village, co-authored by Clemente, found that inhabitants who had no documented contact with Western society possessed more diverse skin microbiomes than United States residents. Clemente attributes this difference partly to lifestyle factors, particularly increased outdoor exposure with minimal clothing coverage.

This finding aligns with observations of other nature-connected communities. Aki Sinkkonen, principal scientist at the Natural Resources Institute Finland, notes that groups like the Amish, who maintain high levels of environmental contact, experience lower allergy rates.

Sinkkonen's research provides additional evidence for nature's impact on microbiome health. In a 2020 study, researchers added forest floor and sod materials to urban day-care centers. After 28 days, children at these nature-enriched centers showed increased skin microbe diversity, reduced inflammatory markers in their blood, and higher levels of regulatory immune cells.

A subsequent study published this year examined indoor gardening's effects on healthy urban adults. Participants who worked with microbe-rich soil demonstrated greater skin microbiome diversity and increased anti-inflammatory substances in their blood compared to those using microbe-poor soil.

While more research is needed to determine the longevity of these effects and their direct relationship to disease prevention, Sinkkonen advocates for regular interaction with microbiome-diverse environments. He emphasizes that passive exposure, such as walking through a park, may not suffice. Instead, he recommends direct contact with plants, soil, or animals for optimal benefits.

Environmental factors can also negatively impact the skin microbiome. Cezmi Akdis, director of the Swiss Institute of Allergy and Asthma Research and professor at the University of Zurich, warns that harsh chemicals can damage the skin barrier. This damage allows disease-causing organisms to penetrate deeper into tissues, triggering inflammation that could become systemic over time.

Akdis notes that many cleaning products and antibiotics can eliminate beneficial skin bacteria, which require significant time to repopulate. This reduction in beneficial microbes can create opportunities for harmful organisms to proliferate and promote the growth of chemical-resistant bacteria, fungi, or viruses.

While maintaining cleanliness remains important, Akdis suggests reducing cleaning frequency and limiting antibiotic product use. He recommends avoiding products containing harsh chemicals, particularly sodium lauryl sulfate, a known skin irritant present in many cleaning products.

Product pH levels also influence skin microbiome health. Kit Wallen Russell, co-founder of the Skin Microbiome School, explains that skin maintains a naturally acidic pH averaging 4.7, which helps defend against harmful pathogens while supporting beneficial microbes. "The skin is quite delicate and if you change these biochemical conditions, you can really decrease biodiversity and cause things like skin irritation, barrier defects and drying out the skin," said Wallen Russell.

Researchers face challenges in analyzing skin microbiome samples due to significant variations between individuals and body locations. "The skin microbiome is famously personalized and site specific," said Oh. While scientists work to develop treatments for imbalanced skin microbiomes, the effectiveness of topical probiotic products remains unclear.

Current scientific understanding suggests a conservative approach to skin microbiome maintenance. Oh recommends focusing on avoiding harm to the skin while seeking exposure to diverse biological environments. "Enjoying the outdoors, having your kids get dirty and not going overboard with sanitizing everything is good for the proper development of the immune system," she said.

As research continues, scientists hope to better understand the skin microbiome's role in health and disease prevention. This knowledge could lead to improved treatments for various chronic conditions while highlighting the importance of maintaining a balanced relationship with environmental microorganisms.