The immunosuppressive effect of ultraviolet (UV) light is evidenced by the inhibition of contact hypersensitivity (CHS) reactions after allergen application on UV-exposed skin. Recent studies indicate that probiotics have immunomodulatory functions in skin. Lactobacillus johnsonii (La1, NCC533) is a probiotic that has shown potential in maintaining the skin’s defense mechanisms, regulating the immune system and enhancing recovery from photo-induced damage. Our objective was to investigate the effect of dietary La1 supplementation on UV suppression of CHS response to dinitrochlorobenzene (DNCB). Caucasian males aged 20-40 years, with Fitzpatrick skin types (FST) II-III were enrolled in a double-blind randomized controlled trial. Subjects were randomized into two groups taking oral preparations of either placebo (maltodextrin) or La1 (1 x 109 CFU). After 8 weeks of oral intake, UV exposure to the upper buttock area was initiated on each subject, using a 1 kW solar simulator with bis81017/WG320 and UG11 filters, followed 2-3 days later by DNCB sensitization. DNCB challenge was performed 2 weeks later on the arm. Both skinfold thickness (SFT) measurement and visual evaluation of CHS (the North American Contact Dermatitis Group or NACDG scoring) were performed. Ninety-Six men completed the study, (48 placebo, 48 La1). There was a significant difference in the CHS response between the two groups in the subjects who received 2 minimal erythema dose (MED), in favor of the La1 group, indicating the capacity of La1 to protect against UV suppression of skin immune responses. Our data suggest that the La1 oral probiotic decreased UV-induced immunosuppression of the skin.
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