Recurrent infections of herpes simplex virus in the orolabial area are known as recurrent herpes labialis (RHL). Vitamin D has been shown to have an important immunomodulatory role and to be associated with several infectious diseases. This hospital-based case-control study aimed at investigating the association between vitamin D and RHL by comparing vitamin D levels in individuals with and without RHL. Individuals who presented to the dermatology clinic at a state hospital due to RHL (n = 50) and matching control group of healthy volunteers (n = 51) were studied. Their vitamin D levels were measured, stratified based on clinical guidelines, and compared. The average serum vitamin D (25-hydroxyvitamin D) levels were 23.8 ± 15.5 and 42.0 ± 26.3 nM in the patient and control groups, with significant differences between their average serum vitamin D levels and vitamin D status. The studied population had serious vitamin D deficiency regardless of having RHL, with vitamin D levels below the adequate limits in more than 96% of the population. Most importantly, the study established a significant association between low serum vitamin D levels and the presence of RHL. Further interventional and pathophysiological studies should clarify the nature and mechanism of the relationship.
Keywords: herpes simplex virus; immune system; recurrent herpes labialis; vitamin D.