Healthy Microbiome for Healthy Infant Skin Development

The Microbiome

A biologically active organ, the skin is home to diverse microorganisms. These microorganisms, together with their collective genomes, form the skin microbiome.

While the specific roles of the native skin microbiome are still an active area of research, evidence indicates that it plays an important role in:

- Preventing colonization by pathogenic microorganisms
- Modulation of skin barrier function, skin immune system

Colonization of Infant Skin

While infant skin is sterile in utero, it is rapidly colonized within days after birth.

Early skin microbiome generally has low diversity, although this may vary, depending on the mode of delivery (via vaginal birth or Caesarean section).

As the infant advances further in age and is exposed to environmental factors, microbiome diversity increases.

The philum Firmicutes remains predominant throughout infancy.

Other dominant phyla include:
- Actinobacteria
- Bacteroidetes

The most common genera are:
- Streptococcus
- Staphylococcus
- Propionibacterium
- Prevotella
- Corynebacterium

Diversity of Microbiome in Adulthood

By adulthood, the skin microbiome has reached a high level of diversity, being composed of (at least): 

- Actinobacteria (dominant phylum)
- Firmicutes
- Proteobacteria

The most common genera are (in order):

- Propionibacterium
- Staphylococcus
- Streptococcus 

The skin microbiome contributes not only to maintaining the homeostasis of the barrier function, but also in modulating the inflammatory responses of infant skin.

Skin cells are involved in both innate and acquired immunity.

Keratinocytes and cutaneous Langerhans cells and T cells interact with the skin surface microbes. These interactions enhance some immune processes, such as:

- Cell recruitment
- Cell activation

One example of this is the interaction of commensal bacteria (e.g. Staphylococcus epidermidis) with skin immune cells.

This interaction:

- Amplifies immune defense against pathogenic microbes
- Aids skin barrier maintenance
- Modulates inflammatory responses

Supporting Microbial Diversity of Infant Skin Microbiome

Given the important role of a balanced skin microbiome on the immune system of infants, extra care should be given to interventions that could alter the composition of the skin microbiome.

It is well-established, for example, that the skin microbiome in infants is optimized at a mildly acidic environment, which also inhibits the growth of pathogenic microbes.

The impact of a prescribed baby skincare regimen, which included a mild baby wash, baby shampoo, and baby lotion, on the skin microbiome of neonates was tested in a clinical study.

- Group A:
  Infants using prescribed regimen for 30 days
- Group B:
  Infants using typical baby skincare regimen, also for 30 days

At the end of the 30 days, microbial diversity of Group A significantly increased when compared to Group B.

Link between Allergy and Atopy with Skin Microflora Changes

According to the Hygiene Hypothesis, increased allergy and atopy among individuals living in industrialized countries may be explained by:

- Oversanitization (as in the case of overcleansing)
- Antibiotic use

An offshoot of this hypothesis suggests that hygiene-associated changes in skin microflora during infancy may be associated with the development of atopic eczema in genetically predisposed individuals.

The early development of atopic diseases may, in turn, contribute to the future risk of asthma.

In contrast, studies have shown that early-life exposures of infants to commensal staphylococci and other microbes are associated with a lower risk of atopic dermatitis and asthma.