Atopic dermatitis (AD) is a chronic relapsing inflammatory pruritic skin disorder, mostly seen in the first six months of life in approximately 45% of patients.

Infants, who have a positive family history of allergic disease, such as asthma, allergic rhinitis or first-degree relatives with AD, have an increased risk of developing AD as compared to infants without any family history of allergic disease.

AD is a multifactorial disease that includes different disease phenotypes below a single diagnosis. AD is mostly characterized by impaired skin barrier function that might lead to clinical skin lesions in infants. The impaired skin barrier function stimulates altered microbial colonization of allergic skin.

Cultivation studies have reported that Staphylococcus aureus inhabits the lesional and non-lesional skin of AD patients in 91–100% and 31–78%, respectively, however only 10% in the skin of healthy individuals. The importance of altered bacterial colonization in AD is revealed by the positive correlation between AD severity and density of cutaneous S. aureus colonization.

Skin emollients are an essential component in the treatment of AD as they can rehydrate the skin, improve the skin barrier function and decrease the severity of AD. Additionally, emollients might also prevent the development of eczema when used regularly in the first six months of life and in infants who are at high risk for AD. The effects of the emollients and their components might modify the skin bacterial growth and its survival.

A trial was conducted to examine the effects of a single type of emollient on features of skin barrier and bacterial 16S rRNA gene sequences in an infant population who are at risk of developing AD.

The skin barrier parameters, bacterial 16S ribosomal RNA gene sequences of cheek, volar and dorsal forearm samples from 6-month-old infants, AD development with a family history of allergic disease were randomized to use emollients (n = 11) or no emollients used (controls, n = 12). Emollient application was initiated within 3 weeks of birth to all body surfaces except in the scalp and diaper area for almost 6 months. Both the randomization groups got the same general instruction regarding correct bathing techniques and to avoid soap. The results of this analysis are as follows:

• The emollient group had a lower skin pH as compared to the control group.
• The number of bacterial organisms in the emollient group was greater as observed in the control group of all sites of the body.
• The Streptococcus salivarius proportion was greater in the emollient as compared to the control groups at all body sites.
• S. salivarius proportion was also observed to be higher in infants without AD as compared to infants with AD.
• A reduction in the abundance of S. salivarius was also recognized in a distinct larger population of big children, which demonstrated an inverse correlation between AD severity at selection sites and S. salivarius proportions.

The study concluded that the reduced skin pH and the increased proportion of S. salivarius associated with the long-term emollient use in infants who are at risk of developing AD might contribute to the protective effects of emollients in high-risk infants.

Source: Glatz M, Jo JH, Kennedy EA, et al. Emollient use alters skin barrier and microbes in infants at risk for developing atopic dermatitis. PLoS One. 2018;13(2):e0192443. Published 2018 Feb 28. doi:10.1371/journal.pone.0192443