Intestinal microbiota: what is it? How does it affect our skin?We live in a microbial world: there are more bacteria on your hand than humans on earth, and our own body is an ecosystem, since we have more bacterial cells in the intestines than human cells in the body. Without bacteria, there is no life.

The set of microorganisms housed in our body is called microbiota, and their genes outnumber human genes by a large margin. Many specialists have begun to call the bacterial microbiota our second genome: approximately two kilograms of bacteria in continuous evolution live in our intestine. Furthermore, while our human genome is fixed, the bacterial genome is malleable, changing the proportion and number of bacteria we host. 

What are the functions of our microbiota?

Bacteria co-evolved with us along millions of years, so at the end our body delegated part of our biological functions to them. Some of these functions are:

  • They help our immune system and inflammatory response. This is why many autoimmune diseases are caused by imbalances in the intestine.
  • They prevent the attack of harmful bacteria. A weak microbial ecosystem facilitates the colonization of dangerous microbes, and we get or feel sick. 
  • They feed us and protect us from disease, for example by producing a fatty acid called butyrate from molecules that we cannot digest ourselves. This short-chain fatty acid has been shown to provide energy in the form of usable calories and protects us against diseases such as colon cancer and obesity. 
  • Since bacteria can synthesize compounds by themselves, they also participate in the synthesis of some vitamins and essential amino acids for our body.

What problems can we have for having a poor quality microbiota?

Not only external factors affect our health (excessive sun exposure, tobacco, pollution, lack of exercise…) but also our microbiota. Many modern diseases start or are related to a poor quality or imbalances of the intestinal microbiota, coming together with one of the following intestinal problems.


Dysbiosis (also called dysbacteriosis) is the imbalance of the microbial balance of normal microbiota, due to quantitative or qualitative changes in their composition, changes in their functioning or metabolic activities, or changes in their distribution.

Intestinal permeability 

The microbiota is the first line of defense of the intestine. Behind it, there is a thin intestinal mucosa, whose objective is to allow the absorption of nutrients. Problems in this barrier allow the passage of harmful substances.

Small intestine bacterial overgrowth (SIBO)

Intestinal bacteria should be concentrated in the colon, but in some cases they overgrow and colonize the small intestine.

intestinal microbiota problems

Causes of microbota imbalances

The three previous microbiota problems are caused in 90% of the cases by the factors listed below:

  • Poor nutrition during our first months of life. The bacterial colonization starts during our first months of life and has a great impact on the future health. Lack of natural breastfeeding impacts directly on the microbiota of the baby.
  • Industrial food. Our genes are not well adapted to modern food, and neither are our bacteria.
  • Excess of medication. Antibiotics and anti-inflammatory drugs such as ibuprofen worsen the health of many people by damaging their microbiota (because they kill both good and bad bacteria). They are basic for our well-being, but they should be used with moderation. 
  • Stress. Permanent stress and lack of sleep negatively impacts the microbiota and favors intestinal permeability.
  • Toxicity. We are exposed to a multitude of new compounds: emulsifiers, conservatives, sweeteners, bisphenols…which alter the intestinal microbiota.

The microbiota on the skin

intestinal microbiota skin problemsNot only the intestines are a microbiota environment. The skin is composed and covered by hundreds of species of living microorganisms, organized in a very specific way. An alteration of this balance can cause a skin disease. 

The cutaneous microbiota evolves progressively and varies from one individual to another according to: 

  • Age (birth, puberty, old age)
  • Sex (male/female)
  • Genetic factors
  • Psychochemical factors (humidity, pH, temperature, lipid content of the skin)
  • Environment (climate, geographical location)
  • Lifestyle (hygiene, cosmetic products, socio-economic conditions, etc.)
  • State of the immune system
  • Existence of diseases or taking medication 

It also differs in the same person, according to the place (face, armpits, back, etc.). Its imbalance is always related to dermatological diseases such as acne, psoriasis or atopic dermatitis.