The use of topical cosmetics, soaps and toiletries on the skin may have a profound negative impact on the microbiome. The excessive use of antibiotics, handwashing or lotions, for example, may alter the microbial community and create an opportunity for skin pathogens to colonize the skin. Now, that does not mean we stop handwashing – it is still necessary and highly recommended.
Topical antibiotics bacitracin, neomycin and polymxin (all prevent bacterial infections on skin where there are small cuts, scrapes or burns) were shown to create drastic shifts in the skin microbiome, compared with the antiseptic treatments ethanol or iodide.
Antibiotic-treated mice were shown to be more susceptible to S. aureus infection which can cause disease. S. aureus is damaging to the skin as it can product virulence factors, lysins and proteases plus it can disrupt the epidermal barrier.
As another example, occluding skin abrasions with bandages or other barriers may promote an overgrowth of potentially pathogenic anaerobes—S. aureus, for example.
In yet another study, topical cosmetic use was associated with a higher Propionibacterium concentration, (potentially causing acne) but the results varied by skin hydration levels in the study subjects.
While not all cosmetics negatively affect the skin microbiome, the potential impact of topical cosmetics on the microbiome must be considered during product development, as disruptions in the microbiome clearly impact skin health. Most notable are the effects of antibiotics that can create opportunities for the entry of S. aureus, which could be problematic.
In the antiseptic tests, however, neither the alcohol or povidone-iodine groups of mice experienced microbial change dramatic enough to be clustered into microbiome-based groups, as there was no discernible difference in the number of bacteria strains of the control and test groups.
While at varying degrees, both treatments ultimately removed bacteria that competes with the pathogenic S. aureus, which could lead to skin infections. In relation, researchers have already begun tests in human subjects to understand if there are similarities in how human skin works against infection.