Abstract:

As the body’s largest organ, skin is the home of billions of microbes and helps protect the host from the external pathogens. The skin microbial barrier can be affected by endogenous factors （skin location, age, gender, and race） and exogenous factors （environment, antibiotics, and cosmetics）. Cosmetics contain complex ingredients, such as preservatives, fragrances, emulsifiers, moisturizers, etc. These substances may affect the skin’s microenvironment. The purpose of this study is to investigate the effects of a cream containing fresh milk on the bacterial diversity of facial skin using high-throughput sequencing technology. A total of 10 subjects were enrolled and they were all females with the average age of 24.1 years old. The subjects used a cream containing fresh milk for 28 days, and the cheek skin microbiological specimens were collected by cotton swabs before and 28 days after the use of the fresh milk cream. DNA was extracted and amplified by PCR, and 16S rRNA high-throughput sequencing was carried out. OTU clustering and species classification annotation were performed to analyze and compare the bacterial community composition, diversity and differences of the facial skin before and after using the fresh milk cream. It is found that after using the fresh milk cream, the alpha diversity parameters including Chao1 and Shannon diversity index of the cheek skin decrease, and the distribution of the samples becomes more concentrated. The species composition at phylum level after using the cream is the same as the baseline, indicating that the use of this cream has little impact on the skin microbial health. However, the proportion of Firmicutes and Actinomycetes in the skin flora of the subjects after using the cream significantly increase, which is mainly caused by the increase of the proportion of Staphylococcus and Propionibacterium, respectively. The Staphylococcus resides in the skin area that is rich in moisture, whereas Propionibacterium plants in the area with abundant sebum content. Additionally, no skin adverse reactions are observed among the subjects, showing that the fresh milk cream is generally well tolerated. Taken this, the study reveals that the fresh milk-containing cream plays an important role in regulating the microecology of the facial skin, and has a prominent moisturizing and nourishing efficacy.

Key words: skin, fresh milk cream, bacterial diversity, high-throughput sequencing technique