The microbiome is the first and foremost protective barrier that keeps the skin healthy. This is an ecosystem consisting of a billion microorganisms (bacteria, fungi and viruses) that settle on the skin at birth - this is how an individual microbiome is created for each person.

When the protective reaction of the body is weakened the activity of “bad” bacteria increases so increases the risk of developing diseases such as acne and rosacea. In parallel with this faster aging of the skin happens with a decrease in immunity. It loses the ability to self-repair. Visible signs of a disrupted microbiome are inflammation, dehydration, dull skin tone, and increased skin sensitivity.

Let's say right away that probiotics in their pure form are not used in cosmetics since living microorganisms are extremely unstable and they need a special nutrient environment that is not at all like a face cream. Cosmetics with live bacteria would be stored no longer than kefir. The composition of probiotic products includes as a rule fragments of microorganisms - lysates, which have the same effect as the microorganisms themselves; enzymes or other substances needed by the skin produced by bacteria.
There is no reason to doubt the effectiveness of lysates - vaccines and serious drugs are created in a similar way in which exactly the necessary fragments of microorganisms work.