The skin microbiome is influenced by a variety of factors, both intrinsic (internal) and extrinsic (external). Here’s a detailed look at the key factors affecting the skin microbiome:

Intrinsic Factors

1. Age: The skin microbiome changes throughout different life stages:

• Infancy: Newborns have a unique microbiome influenced by the mode of delivery (vaginal birth vs. cesarean section).
  
  
• Adolescence: Hormonal changes during puberty can alter the microbiome, often increasing oil production and changing microbial composition.
  
  
• Adulthood: The microbiome stabilises but can be influenced by lifestyle and health.
  
  
• Elderly: Aging can lead to changes in skin structure and immune function, affecting the microbiome.

2. Gender: Hormonal differences between males and females result in different skin microbiomes. For instance, males typically have higher sebum production, which can influence the types of bacteria present.

3. Genetics: Individual genetic makeup affects skin properties such as oil production, moisture levels, and immune responses, all of which influence the microbiome.

4. Skin Site: Different areas of the body have distinct microbiomes due to variations in skin environment (e.g., oily vs. dry areas, presence of hair follicles).

Extrinsic Factors

1. Environment: Climate (humidity, temperature), pollution, and UV exposure can significantly impact the skin microbiome.

Urban vs. Rural: People in urban environments may have different microbiomes compared to those in rural areas due to varying levels of pollutants and lifestyle differences.

2. Hygiene and Skincare Practices: The frequency of washing, the use of soaps, lotions, and other skincare products can disrupt or support the natural microbiome.

Antibacterial Products: Overuse can kill beneficial bacteria along with harmful ones, disrupting the microbiome balance.

3. Diet and Nutrition: Diet can influence the microbiome by affecting skin health and immune function. For instance, diets high in sugar and fat may promote conditions like acne, which are associated with specific microbial changes.

4. Health Status and Medical Conditions: Chronic conditions such as diabetes, atopic dermatitis, and psoriasis can affect the skin microbiome. Immunocompromised individuals often have altered microbiomes.

5. Medications: Antibiotics and other medications can disrupt the skin microbiome. Antibiotics, in particular, can reduce microbial diversity by killing both harmful and beneficial bacteria.

6. Lifestyle Factors: Exercise, stress levels, and sleep can indirectly affect the skin microbiome by influencing overall health and immune function.

7. Contact with Others: Close physical contact with other people or animals can lead to the transfer of microbes, influencing one's skin microbiome.

Understanding these factors is crucial for developing strategies to maintain a healthy skin microbiome, which is essential for overall skin health and disease prevention.