Frequent bathing may compromise skin barrier integrity in infants, study data published in the Journal of Allergy & Clinical Immunology suggests. In a cohort of babies aged 3 months, a dose-response relationship was observed between bathing frequency and increased prevalence of atopic dermatitis (AD).

Investigators conducted a cohort study of 3-month-old babies from England and Wales. Parents were invited to complete an online questionnaire at baseline and when their baby turned 1 year old. The questionnaire captured bathing frequency as a categorical variable, with the following options: “hardly ever”; “once a week”; “2-4 times a week”; “5-6 times a week”; “daily”; and “more than daily.” The use of moisturizer, shampoo, soap, bubble baths, bathing oils, and baby wipes was also assessed. The questionnaire also asked respondents to report race/ethnicity, family history of skin problems, and water hardness in their living situation. Transepidermal water loss (TEWL) was measured on the patients’ left forearms at 3 and 12 months of age. Skin barrier dysfunction was defined as TEWL ≥15g/m2*h. AD was ascertained by parental report. Logistic regression was used to assess the relationship between AD and bathing frequency. In these analyses, bathing frequency was binarized as “weekly or less” or “more than weekly.”

The study cohort comprised 1303 heathy, 3-month-old infants. At baseline, the overall prevalence of AD was 24.4%. The prevalence was greatest in patients bathed at least daily (44.0%). In patients bathed weekly or less, the prevalence of AD was just 14.6%.  In regression models, bathing more than weekly was associated with significantly higher odds of AD than bathing weekly or less (odds ratio [OR], 1.98; 95% confidence interval [CI], 1.06-3.71). Median TEWL at baseline was 12.8 g/m2*h; median TEWL was higher in patients with AD compared with those without (15.7 vs 12.4 g/m2*h; P <.001). Babies who were bathed weekly or more had a greater risk for skin barrier dysfunction than their comparators bathed up-to-weekly (OR, 2.53; 95% CI, 1.38-4.62). The greatest odds for skin barrier dysfunction were observed in the daily bathing group (OR, 4.32; 95% CI, 2.27-8.22; P <.001) compared with up-to-weekly bathing. In sensitivity analyses which excluded infants with AD or dry skin at baseline, the same relationship was observed of TEWL and daily bathing (OR, 1.02; 95% CI, 1.01-1.03; P <.001). The relationship of elevated TEWL and higher bathing frequency was maintained at 12 months (P <.001). However, AD prevalence at 12 months was not significantly associated with bathing habits.

In this cohort study of infants, bathing frequency had a dose-response relationship with skin barrier dysfunction at both 3 and 12 months of age. Bathing frequency was associated with AD prevalence at 3 months only. These data suggest that increased bathing frequency may negatively affect the developing skin barriers of infants. “[F]uture studies should investigate the impact of the length of time babies are bathed for and whether moisturizer application directly after bathing can ameliorate the negative effect on skin barrier function,” investigators wrote.


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Disclosure: Several study authors declared affiliations with the pharmaceutical industry.

Please see the original reference for a full list of authors’ disclosures.

Reference

Marrs T, Perkin MR, Logan K, et al. Bathing frequency is associated with skin barrier dysfunction and atopic dermatitis at three months of age [published online April 26, 2020]. J Allergy Clin Immunol. doi: 10.1016/j.jaip.2020.04.043