Background: Herpes labialis is the result of the presence of Herplex Simplex Virus -1 (HSV-1) and is a common disease in the population. Because of its visibility it has a serious impact on social life and the feeling of well-being in people who suffer from this disease. Until now there is no effective treatment and no remedy for prevention of the virus outbreak.

Prebiotics and probiotics have both been shown to have a favorable and supportive effect on the immune system in different health conditions such as influenza, atopic dermatitis and diarrhea. So far no study has addressed the effect of the consumption of pre- and/or probiotics in a population with recurrent herpes labialis.

Aim of the study: The present study investigated the effect of pre- or probiotics or a combination of the two on the recurrence of herpes labialis lesions as well as on the immune system in general.

Design: 78 Patients were eligible to participate in the study and after a run-in period of two weeks consuming a placebo minidrink were randomized to one of the four experimental groups, these were: placebo minidrink (n=), prebiotic (fructooligosaccharides) minidrink (n=), probiotic (Lactobacillus rhamnosus GG or LGG) minidrink (n=) or a minidrink containing a combination of a pre- and probiotic. These minidrinks were consumed for another 5 weeks. At day 33 of the study the lip most prone to the development of a lesion was stimulated with UVB in order to provoke a lesion. During the entire study period subjects were checked for any clinical signs of a lesion, completed a self-assessment regarding the lesion and a quality of life questionnaire at baseline (day 14) and the end of the study (day 49). In addition, a blood sample was collected at baseline and at the end of the study to be analyzed for general and HSV-specific antibodies, intracellular cytokine concentrations and parameters of the innate immune response such as natural killer cell activity and phagocytosis.

The present study showed that the daily consumption of a minidrink containing either only Lactobacillus rhamnosus or a combination of Lactobacillus rhamnosus and fructooligosaccharides significantly decreased both the occurrence and the incidence of Herpes labialis lesions after stimulation with UVR in a population with recurrent Herpes labialis. No difference in the function of either CD8+ T lymphocytes or natural killer cells was found, nevertheless a trend, that did not reach statistical significance, was observed for some of the immunological analyses pointing out towards an immunemodulating effect of probiotic or pre- and probiotic combination minidrink on the adaptive immune system. The end of study results of immune analyses were slightly improved compared to the baseline values in individuals using the probiotics or the pre- and probiotics combination minidrink, however the differences between groups did not reach the significance level. Phagocytosis and killing were clearly and statistically different in individuals that used either placebo or probiotics or pre- and probiotics minidrinks. Therefore, the probiotics and the pre- and probiotics minidrinks have an important effect on innate immunity, resulting in a significant improvement of both phagocytosis and killing. No effect was found on the quality of life of subjects. No special or unusual features of the safety evaluations were found. No serious adverse events were reported during the study.

Inclusion Criteria:

• Healthy free-living men and women aged 18 to 65 years-old
• History of recurrent herpes labialis at most 3 episodes after exposure to sunlight in the previous 12 months
• Fitzpatrick skin type 1 to 4
• No presence of herpes labialis lesion at the time of recruitment
• Consent to the study and to comply with study product
• Agreement to adhere to the prescribed list of food and nutrients as provided at the start of the study

Exclusion Criteria:

• Presence of acute/terminal disease
• Intolerance for milk protein or lactose
• Daily consumption of probiotic products 1 month before start of the study
• Treatment with acyclovir or other medication believed to interfere with immune responses at the time of the study
• Participation in any herpes UVB reactivation study within the previous three months
• Episode of herpes labialis within 30 days before enrolment in the study