When we think about the skin, we usually relate it to beauty. However, it is important to understand that the main function of the skin is not to help us look beautiful and attractive, but to help to protect our body. So how does the skin perform this function and how we can contribute to this process?
Skin microbiome is the skin area (with its physiological characteristics) together with millions of microorganisms living on it.
Skin microbiome plays a key role in keeping the skin healthy, controlling common skin diseases, and even protecting the body against infections.
Only a balanced skin microbiome demonstrates a benefit to the body.
Proper care of the skin helps to ensure a balanced skin microbiome.
The skin microbiome is millions of microorganisms colonizing the skin together with their environment (the skin area where they live and its physiological characteristics). Although it is hard to believe, but all these beneficial bacteria, fungi, yeasts, and viruses living on the skin are necessary for the skin to optimally perform its main function; to ensure the external physical barrier between the human body and the environment.
Functions of skin microbiome
Skin microbiome helps to ensure protective function in two ways:
- Protecting our body against bad microorganisms. Skin is the largest organ in the body, having the major daily contact with the environment, as well as, the most frequent contact with microorganisms that live around us. Therefore, it may seem that the skin is the “dirtiest organ” which harbors all these microbes. However, the opposite is true, skin microbiota produces bioactive molecules attractive for beneficial bacteria growth, thus leaving no space for all these bad microscopic creatures to successfully settle in the skin.
- Acting as a protective shield against external aggressors. All microorganisms living on the skin form a thin, invisible layer that covers the skin surface. Thanks to this layer, the skin is protected from direct contact with aggressors experienced daily, like air pollution, UV, etc.
Skin microbiome dynamics
Until the person fully matures, their skin microbiome is quite a dynamic system, which undergoes two dramatic changing stages:
- Birth. This stage is mainly dependent on the birth mode. Neonates delivered vaginally obtain the microbes that colonize the vagina, while babies born via the Caesarian section acquire microorganisms that are associated with the adult human skin. However, until now, the long-term effect of these initial skin colonization modes remains unknown.
- Puberty. This stage appears during puberty and sexual maturation. Throughout this period the increased hormones levels stimulate the sebaceous glands (microscopic glands located in hair follicles) to secrete larger amounts of sebum (an oily, waxy substance, which mixes with fat molecules ((lipids)) to moisturize and protect the skin). This supports lipophilic bacteria proliferation. Thus, after puberty, the person's skin is enriched with lipophilic microorganisms. However, the question whether new bacteria strains are acquired or just the existing microorganisms amount changes that occur during adolescence still remains unanswered.
It is considered that after these phases, a healthy adult person's skin microbiome remains relatively constant throughout a lifetime. However, it is important to notice that small variation in the microbiota composition still occurs. Due to the alterations of skin characteristics in the different parts of the body (skin temperature, humidity, sebaceous gland density, pH, etc.) distinct ecological niches are created. In these niches' composition of microbial communities differs, e.g., oily skin areas are dominated by lipophilic bacteria species, whereas microorganisms that thrive in humid environments are preferentially abundant in moist sites.
Skin microbiome and diseases
Thus, the microorganisms living on the skin are extremely important in contributing to the body's defense system. Besides, under certain circumstances, microbiota, which naturally is beneficial to the organism, can even become pathogenic. This usually happens when one bacteria type begins to dominate and reproduce intensively, leading to the out-competition of other microorganisms. This process is called microbiota dysbiosis and can initiate the onset of many common skin diseases.
The table below shows the main diseases associated with skin microbiome.
|Disease type||Key findings|
|Acne vulgaris||Acne is a chronic, inflammatory skin disorder affecting more than 85% of adolescents and young adults. It is associated with the increased proliferation of bacteria P. acnes. Increased sebum production during puberty creates an environment attractive for P. acnes proliferation.|
|Psoriasis vulgaris||Psoriasis is an immune-mediated disease that causes erythematous and scaly plaques on the skin due to chronic inflammation. It was determined that microorganism composition alterations exist in the plaques: the increase of Corynebacterium, Staphylococcus, and Streptococcus; decrease of Malassezia, Propionibacterium, Cutibacterium.|
|Atopic dermatitis||Atopic dermatitis is an inflammatory skin disease affecting 15% to 20% of children and 2% to 10% of adults. It causes redness and irritation of the skin. It is associated with S. aureus skin colonization/infection, and increase in Streptococcus, Propionibacterium, and Corynebacterium microorganisms in the sites of skin lesions.|
|Chronic wound||A chronic wound is a skin disorder when the wound repair process fails, and it does not heal in an orderly set of stages within a predictable amount of time (the way most wounds do). This disease is prevalent in the elderly, as well as in patients suffering from diabetes and obesity. Skin microbiota dysbiosis is associated with the wound healing process, as elevated amounts of S. aureus and Pseudomonas aeruginosa are detected in chronic wounds.|
Despite the identified skin microbiome alterations in various skin diseases, it is still unclear if microorganisms play a causative role or are just a consequence of the inflammatory microenvironment. Thus, more studies are needed to be performed to fully understand how microbiome dysbiosis is associated with the genetic and environmental factors which also contribute to the onset of these diseases.
How to take care of the skin microbiome?
Although science has not yet fully clarified whether the skin microbiota is the main reason of the onset of various skin diseases, it is pretty clear that in order to reduce the outcome of appeared skin disorders we must maintain/restore the skin microbiota balance.
Two ways can be distinguished how to take care of damaged skin microbiome: traditional treatments and healthy lifestyle.
The main target of these treatment methods is inflammation. The treatments are usually prescribed by a doctor, e.g., various drugs (antibiotics, retinoids, etc.), and non-invasive therapies (low-level laser (light) therapy, etc.). These treatments are quite effective, however, like most drugs, they can demonstrate some side effects.
Scientific studies have proven that a healthy diet, sports, and proper personal hygiene are important to keep the skin microbiota in balance.
In the case of nutrition, it was proven that there is a positive correlation between what we eat and how our skin looks, the so-called gut–skin axis. For example, acne disease severity is associated with high-glycemic-load foods. These foods elevate bioactive molecules (insulin, insulin growth factor-1, etc.) levels, which stimulate increased sebum production and finally lead to the onset of acne.
Sports are also extremely important for healthy microbiota maintenance. The sweat released while exercising reduces the thinning of the stratum corneum (the outermost dead skin layer), i.e., the constant environment necessary for the existence of microorganisms is maintained.
Personal hygiene is also closely related to the onset of diseases. Too much washing/bathing and using too many skincare products may change the normal state of the skin (pH, oiliness, etc.) and cause microbiota dysbiosis. Thus, it is important to build up your consistent, intentional skincare routine that nourishes the skin. It is recommended to use natural skin care products with as few ingredients as possible, and of course not to use tons of different products at once. Everywhere, balance must be retained.
The skin microbiome is a developing area for research, and more studies are needed to fully understand how these microorganisms living on us affect our health and what we can do to make them feel good. Although current research shows that microbiome misbalances could be linked to various skin conditions, it is still not clear whether they are the cause or consequence of the diseases. Thus, if you have any doubts about your skin condition, it is advisable to consult your dermatologist first before attempting to self-medicate.
- Nature Reviews Microbiology. The human skin microbiome.
- Microbial Cell Factories. Advances in the human skin microbiota and its roles in cutaneous diseases.
- Frontiers in Cellular and Infection Microbiology. The Human Skin Microbiome in Selected Cutaneous Diseases.