by Heather Lasseter, PhD, Medical Writer
The use of antibacterial soaps has long been controversial. According to the FDA, these products are no more effective at preventing illness than ordinary soap and water, and research indicates they may confer bacterial drug resistance.
Lately, the role of the human microbiome has gained exposure, with a primary focus on how altering the gastrointestinal tract’s bacterial community may impact conditions like Crohn’s disease, diabetes, and even obesity. Moving forward, understanding the microbiome of the skin may be equally important for regulating human health and disease.
Bacteria, viruses, and fungi – oh my!
The human skin is the largest organ in the body and represents the first line of defense against invading pathogens. But this physical and chemical barrier is populated by its own inhabitants: a diverse collection of bacteria, viruses, and fungi that preferentially thrive in different habitats of the epidermis. These make up the skin’s “microbiota,” one component of the human body’s complex microbiome. Counting bacteria alone, as many as 1 million microorganisms may inhabit just 1 square centimeter of skin, with distinct populations preferring moist, dry, or sebaceous (oil-producing) environments.
Bacteria commonly found on the skin (commensal bacteria) include Propionibacterium acnes, Staphylococcus epidermidis, Staphylococcus aureus, Corynebacterium diphtheriae, Corynebacterium jeikeium, and Pseudomonas aeruginosa. Under normal conditions, commensal skin bacteria are thought to be beneficial in defending against pathogenic bacteria. Commensal microbes may also either protect from or contribute to diseases like atopic dermatitis, psoriasis, acne, skin ulcers, and cancer.
The skin microbiome has evolved with the host organism, adapting to survive large desiccated regions, areas of acidic pH, the continual shedding of superficial cells, and the host’s immune response. As such, having the right commensal microbial community appears necessary for healthy skin. While acne has long been associated with P. acnes, research indicates acne lesions – in contrast to healthy skin – are additionally colonized by S. epidermidis and Corynebacterium. Similarly, skin samples from patients with psoriasis have higher concentrations of S. aureus compared with those from healthy subjects, but also lower levels of Propionibacterium species.
So what does this mean?
Our antibacterial soaps – not to mention modern cosmetics and hygiene products that change the skin’s natural microenvironment – may fundamentally alter the composition of our friendly bacterial community. According to Audrey Gueniche, a project director from L’Oréal quoted in the New York Times Magazine, buzz surrounding the skin microbiome “has revolutionized the way we study the skin and the results we look for.” And companies are taking note.
- With global patents pending and issued, AOBiome is developing topical treatments that use ammonia-oxidizing bacteria to help replenish bacteria that naturally exist on the skin.
- Scientists from the R&D team at L’Oreal are collaborating on research endeavors to develop skin products that increase so-called “good” strains of bacteria.
More research is necessary to fully understand the long-term implications of altering the skin’s microbial composition, but restoring healthy skin bacteria may provide a unique opportunity to treat serious skin disorders. Probiotics have gained popularity among health-conscious consumers keen on maintaining good gut flora. Perhaps the time has come to consider how we treat, and even cultivate, beneficial skin microbiota.