In dermatology, prevention of the initial development of skin problems, flare ups, and antibiotic resistance now lies firmly within the domain of dermocosmetics. The promotion of the “normal” skin microbiome, using dermocosmetics tailored to specific conditions, can play a key role in this arena.
New technologies, particularly genomics, have only recently shown that the skin is host to far more diverse and dynamic communities of bacteria than previously thought. These colonies are established at birth and are on and in the skin. There are many different skin habitats, for instance, the dry fronts of the leg or the moist underarm, each of which support a different mix of bacterial communities; all of them are in constant flux.
WHAT IS THEIR PURPOSE?
The skin is the body’s first line of defense and its largest immune organ. Therefore, its bacteria are essential to detecting and managing harmful incoming bugs. They not only warn the body of invaders and trigger a response to them, but also self-manage their communities, making sure that no one type of bacteria becomes over dominant. They do this through crowding out, or even direct killing with, antimicrobial peptides (AMPs). The bacteria also help the skin suppress inflammation. A critically important role of the skin microbiome is maintaining an efficient skin barrier function.
Many factors, both external and internal, can affect the skin microbiome, including temperature, hydration, pH, washing, choice of skin product, ultraviolet radiation, stress, hormones, illness, and anxiety. Treatments used to treat skin conditions such as anti-inflammatory and antibacterial treatments may have a profound impact.
A person’s skin microbiome is unique to them. Therefore, the use of other individuals as controls in experiments has no value. New techniques have had to be developed in which the bacteria of unaffected skin is compared to that of adjacent affected skin on the same person.
In general, the more diverse the skin microbiome, the healthier the skin. Microbial imbalance, or dysbiosis, is associated with many skin problems, including psoriasis, atopic dermatitis, and acne.
RESTORING MICROBIAL BALANCE WITH PREBIOTICS
Most people are familiar with the strategies used to ensure a healthy gut microbiome. Prebiotics for the gut do not contain living bacteria, but are foods or substances that are beneficial for the growth of the body’s existing populations of bacteria. Probiotics, by contrast, are supplements, drinks, or foods containing living bacteria, which are introduced into the gut.
As far as skin is concerned, no products for topical use contain living bacteria. Confusingly, preparations for use on the skin that contain dead, whole, or fragmented bacteria have, in the past, also been called probiotics. Now, the consensus is that these preparations should be regarded as prebiotics and the following definition applies. Topical prebiotic formulations for the skin contain ingredients that stimulate the growth or activity of the skin’s own helpful bacteria. They might also contain lysates (treated to break down their walls) of dead harmless bacteria, such as Vitreoscilla filiformis or Lactobacillus sp.
Different skin conditions are associated with different types of dysbiosis, each involving different types of bacteria. Topical prebiotics can be tailored specifically for that condition.
An intriguing possibility for the future is supplements taken by mouth that influence the gut bacteria, which, in turn, influences the skin microbiome. This hope might sound farfetched, but many gut conditions are linked with skin problems. For instance, psoriasis is more common in people with irritable bowel syndrome and celiac disease, and some food metabolites are well known as being secreted through the skin. Onion family plants, such as garlic, that have antibacterial properties are a classic example. How it might change the skin’s microbiome is unknown; much more research is needed in this area to understand it better.