A complex community of bacteria, fungi, viruses, yeasts and mites live normally our skin. An estimated 1 billion bacteria with hundreds of sub-species inhabit every square centimetre of our skin. Most of these micro-organisms are essential for the normal, healthy functioning of the skin. However, some may be pathogenic and will produce skin diseases.
“An estimated 1 billion bacteria with hundreds of sub-species inhabit every square centimetre of our skin”
In utero, a foetus’ skin is sterile but only a few minutes after birth colonization by micro-organisms begins and over time the microbiome develop on the skin with characteristics unique to you as the host. The diversity of the microbiome depends on the skin’s physical and chemical characteristics but also on age, general state of health, immunity, gender, the location on the body, environment, lifestyle and underlying pathology.
In the past the only way that we could identify these micro-organisms was by trying to culture them in a laboratory but this proved to be an inefficient process – for instance less than 1% bacteria that normally live on our skin can be cultured under standard laboratory conditions. DNA Amplification and Sequencing technology has changed all this and we can now identify the myriad of micro-organisms that live on our skin. To date 500 bacterial species have been identified on a healthy skin.
Some are easily seen with a normal microscope – all humans carry two species of Demodex mites and they mainly live in the pilosebaceous units on the face and at the base of the eyelashes in the hair follicle. They are more numerous in patients with an oily skin as they actually live on sebum and it is postulated that an overgrowth of the Demodex mites may cause Rosacea as well as Seborrhoeic Blepharitis i.e. eczema of the eyelids. Mites leave the hair follicles at night as we sleep and walk over the facial skin at approximately 10cm per hour. This is not a pleasant thought but they are generally harmless and play a role in the overall health of the skin!
“Mites leave the hair follicles at night as we sleep and walk over the facial skin at approximately 10cm per hour”
At different sites on the body, different bacteria or yeasts may predominate. The diversity of microbiomes is higher in the folds of the skin, where there is more hair and in areas that perspire.
A bacteria called Corynebacteria tends to live mainly in the moist folds of the skin i.e. often in the armpits and groin. Sweat is actually odourless but this bacteria is able to convert sweat into malodorous chemicals. Therefore, abnormal body odour is caused by an overgrowth of the Corynebacterium in the folds of the skin. The regular use of an anti-bacterial shampoo, for example, Povidine-Iodine (Betadine), can help to control this abnormal body odour – when you shampoo your hair, you can use it on those areas which produce an odour.
“The regular use of an anti-bacterial shampoo, for example, Povidine-Iodine (Betadine), can help to control this abnormal body odour”
A bacteria called Propionibacterium acnes lives in the normal pilosebaceous unit on the face, especially in patients with an oily skin. In patients with acne, the top layer of the skin, the stratrum corneum, becomes more sticky and therefore blocks the entrance to the pilosebaceous unit – this then forms what appears on the skin as a blackhead or whitehead. As a result of this blockage to the entrance of the pilosebaceous unit, one gets an overgrowth of the Propionibacterium acnes in the hair follicle. This results in inflammation of the surrounding area i.e. a red pimple or pustule.
One of the best topical products to counter this inflammation is Benzoyl Peroxide. Obagi CLENZIderm Therapeutic Lotion – this will help to reduce this inflammatory acne without causing bacterial resistance. Topical tea tree oil is also useful for treating the overgrowth of the Propionibacterium acnes – Lamelle Clarity range. Niacinamide used in topical creams has similar anti-inflammatory action SkinCeuticals Metacell Renewal B3 or pHformula VITA B3 Cream.
“Topical tea tree oil is also useful for treating the overgrowth of the Propionibacterium acnes”
Approximately 90% of patients with Atopic Eczema are colonized by the pathogenic Staphylococcus Aureus as opposed to less than 5% Staphylococcus Aureus in healthy individuals. The overgrowth of this bacteria can cause a flare of the atopic eczema/dermatitis and often these patients will require a systemic antibiotic as well as washing with an anti-bacterial shampoo such as the Povidine-Iodine. Once the bacterial infection has been properly treated the flare of the atopic eczema/dermatitis will subside.
Therefore, on the normal healthy skin we have billions of micro-organisms that live happily on our skin but if the normal balance of these micro-organisms or our skin barrier gets upset, then we can get an overgrowth of pathogenic or commensual micro-organisms that can cause skin disease.
La Roche-Posay Thermal Spring Water has been used historically for centuries in the management of chronic inflammatory skin diseases. This thermal spring water is rich in selenium and strontium which have been shown to have anti-inflammatory properties. In addition, this spring water also contains a non-pathogenic filamentous bacteria called Vitreoscilla Filiformis. This bacteria has been modified by the research scientists at L’Oreal to produce a patented active ingredient called Aqua Posae Filiformis.
This Aqua Posae Filiformis is included in all the La Roche-Posay products including La Roche-Posay Lipikar Balm AP+ – it contains Shea butter, Canola oil, Glycerine and Niacinamide. This Lipikar Balm AP+ has been shown to reduce the itch and to prevent flare-ups in patients with atopic dermatitis. It is thought that the mechanism behind this is by restoring the normal epidermal barrier function with the correct emollients (as described above) but by also restoring a healthy skin microbiome. In other words the Aqua Posae Filiformis acts as a skin prebiotic.
Maintaining a healthy skin microbiome is a delicate balance between man, the environment and the micro-organisms that inhabit their own eco-systems on the skin.