Background: An increase in Staphylococcus aureus skin colonization in atopic dermatitis patients resulted from the reduction of cathelicidin production in these patients. Recently, an in vivo study demonstrated that vitamin D could stimulate cathelicidin production. Oral supplements of vitamin D might be beneficial in atopic dermatitis.
Objective: To determine the effects of oral vitamin D supplements on clinical impact including Staphylococcus aureus skin colonization evaluation in atopic dermatitis patients.
Material and Method: Twenty-four atopic dermatitis patients were included in this double-blind, placebo-controlled study.
They were randomly assigned into 2 groups for oral 2,000 IUs/day of vitamin D2 supplement and placebo. The lesional swab culture for S. aureus was done at week 0, 2 and 4. Clinical outcomes were assessed by SCORAD score, mexameter for
erythema index and konometer for conductance were done at week 0, 2 and 4. Serum vitamin D levels were also determined
at week 0 and 4.
Results: Twenty patients completed the protocol. S. aureus skin colonization, SCORAD score and erythema index were
significantly reduced from baseline to week 4 for vitamin D treated group comparing with placebo (p = 0.022, 0.028 and
0.014, respectively). There was an inverse correlation between serum vitamin D levels with S. aureus skin colonization and
SCORAD score (r = -1.0, p<0.001).
Conclusion: Oral vitamin D supplement could reduce skin colonization of S. aureus and demonstrated the clinical improvement of patients with atopic dermatitis.

Keywords: Atopic dermatitis, Vitamin D supplementation, Cathelicidin, S. aureus colonization, SCORAD score