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Types and functions of bacteria present on the skin!

According to a study published in Science Magazine in 2009, there are more than 200 types of bacterial flora in the pores and stratum corneum of human skin, and the number of bacteria that inhabit there exceeds 100,000 per square centimeter of the skin. Typical bacteria are Staphylococcus epidermidis, Propionibacterium acnes, and Staphylococcus aureus.

Staphylococcus epidermidis
Staphylococcus epidermidis is present on the surface of skin and pores. It decomposes sweat and sebum with its own enzymes to produce glycerin and fatty acids. Fatty acids keep the skin within a mildly acidic environment. It also produces antimicrobial peptides to prevent the growth of Staphylococcus aureus, which prefers a mildly alkaline environment. Glycerin produced by Staphylococcus epidermidis retains water in the skin and promotes the barrier function.

Propionibacterium acnes
Almost all types of Propionibacterium acnes cannot grow in an aerobic environment and die there. Therefore, it exists within the pores and sebaceous glands. Similar to Staphylococcus epidermidis, it breaks down sebum into fatty acids and glycerin. However, if the amount of sebum increases or an abnormal condition that blocks the pores occurs, it will overgrow and cause inflammation which in turn causes spots on the skin. It does not develop into acne if it does not grow proliferately.

Staphylococcus aureus
Staphylococcus aureus is found on the surface of skin and pores. Although, it is highly pathogenic among Staphylococcal bacteria, it does not cause skin problems such as skin inflammation unless it grow proliferately. However, when the pH value of skin change toward alkalinity, Staphylococcus aureus increase its numbers which will cause dermatitis. If we leave the damaged skin without proper treatment, it may make the wound purulent and worsen the condition.

In addition to these typical bacteria, fungi (mold, yeast) also exist on the skin. Although there are various bacteria on the skin, the skin can be sustained without troubles and remain with sufficient moist if these bacteria are well-balanced. In other words, in order to keep the skin healthy, it is very important to avoid the destruction of the balance of these indigenous bacteria and the reduction of the number of Staphylococcus epidermidis which supports the barrier function of the skin.

How to maintain the balance of indigenous bacteria on the skin?

A tip for maintaining indigenous bacteria in a good balance is to not reduce the number of Staphylococcus epidermidis. We should be aware of the following points in order to keep them in sufficient numbers.

Avoid ultraviolet rays
UV rays are not good for indigenous bacteria on the skin. It is advisable to take appropriate measures against UV rays, such as wearing sunglasses and a hat with an ultraviolet protection. However, overuse of cosmetics which can filter out UV rays may irritate the indigenous bacteria and affect them adversely. We have to be careful about the amount of cosmetics we use.

Avoid dryness of skin
An appropriate measure for skin dryness is also important. We should keep the skin appropriately moisturized with a skin toner and emulsion. Prolonged bathing can dry out the skin. When the skin is soaked in hot water for a long time, the natural moisturizing factors and intercellular lipids that keep water in the skin leak out more than necessary as well as sebum will be lost beyond necessity.

Avoid excessive washing
Excessive washing of the face and body makes weakens the function of indigenous bacteria. If we wash our face and bodies many times a day or use more than the required amount of facial cleanser or body soap, it will contribute to weaken the action of indigenous bacteria. Also, scrubbing our face or bodies with a towel can damage the skin. It is better to avoid it.

Stop overuse of cosmetics
Even though, it is a measure against UV rays or skin dryness, applying more than necessary amount of cosmetics with an ultraviolet protection, skin toner, and emulsion can bring counterproductive results. Since cosmetics may clog pores and Propionibacterium acnes may subsequently proliferate, we should be aware of the usage of those cosmetics and use them appropriately.

To engage in activities that makes us sweat
Our sweat is an energy source for indigenous bacteria on the skin. Making the body to sweat means providing ingredients for indigenous bacteria to produce a natural moisturizing cream. We should engage in exercises and activities that makes us sweat into our daily life.

It is important to avoid the reduction of Staphylococcus epidermidis in order to prevent the growth of Propionibacterium acnes and Staphylococcus aureus which in turn allows the skin to maintain the barrier function. When the skin is dry, it becomes an alkaline environment that makes it difficult for Staphylococcus epidermidis to exist. We should avoid excessive washing, protect our skin from dryness and UV rays, and maintain the balance of indigenous bacteria.

Credit to: Muneaki Takahata Ph.,D.