In discussing an alternative to antibacterial products for imbalances in cutaneous microorganisms that result in mild acne, xerosis, or AD, Simmering and Breves suggest that "prebiotic actives rebalance the skin microflora while probiotic approaches predominantly consist of applying an inactivated microbial biomass of beneficial bacteria" (Hautarzt. 2009;60:809-14).
Cutaneous Immune Homeostasis
In a 2009 randomized, double-blind, placebo-controlled clinical trial with 54 volunteers, Guéniche et al. set out to ascertain whether the probiotic bacterium L. johnsonii (La1) could influence cutaneous immune homeostasis in humans after solar-simulated UV exposure (twice 1.5 MED [minimal erythema dose]). They showed that La1 consumption contributed to hastening the recovery of allostimulatory function in epidermal cells (Dermatoendocrinol. 2009;1:275-9).
Previously, in 2008, Peguet-Navarro et al. conducted a randomized, double-blind, placebo-controlled clinical trial in 54 healthy volunteers to study the potential impact of oral supplementation with La1 on skin immune status after UV exposure. Subjects received either La1 or placebo during the 6 weeks prior to solar-simulated UV exposure. The investigators found on day 4 after exposure that the allostimulatory capacity of epidermal cells had completely recovered in the La1 group correlating with the normalization of epidermal CD1a expression. They concluded that ingested probiotic bacteria hasten the recovery of skin immune homeostasis after UV-provoked immunosuppression (Eur. J. Dermatol. 2008;18:504-11).
Anti-inflammatory Activity
In 2010, Guéniche et al. demonstrated that B. longum can reduce skin inflammation mediated by substance P (Exp. Dermatol. 2010;19:e1-8). In a separate study, some of the same investigators found that L. paracasei appears to have the capacity to confer benefits related to barrier function and skin reactivity, also blunting the effects of substance P–induced skin inflammation (Eur. J. Dermatol. 2010;20:731-7).
Antiphotoaging Activity
In 2010, Bouilly-Gauthier et al. evaluated the effects of a dietary supplement combining L. johnsonii (La1), which is thought to protect the skin immune system after UV exposure, and nutritional doses of carotenoids on early UV-induced skin damage. They performed three clinical trials using various UV sources (non–extreme UV with a high UVA irradiance, extreme simulated solar radiation, and natural sunlight) in 139 healthy women over age 18 with skin type II-IV. The investigators found over the 10 weeks of the study that the combination of probiotic (La1) and nutritional doses of carotenoids lowered early UV-induced skin damage caused by simulated or natural sun exposure. Further study of the possible long-term effects against UV exposure and photoaging is warranted, they concluded (Br. J. Dermatol. 2010;163:536-43).
Topical Uses
In a study more than a decade ago, Di Marzio et al. showed that the topical application of a cream containing Streptococcus thermophilus, an organism found in most yogurts, raised the production of ceramides, which is notable given the anti-inflammatory activity and antimicrobial activity of some ceramides against Proprionibacterium acnes (J. Invest. Dermatol. 1999;113:98-106;Gut Pathog. 2011;3:1). Two recent in vitro studies have also revealed that probiotics can have antibacterial activity against P. acnes (Int. J. Cosmet. Sci. 2010;32:139-42; J. Microbiol. 2009;47:101-9). The prospects for efficacy of topically applied probiotics in the prevention and treatment of pro-inflammatory immune reactions are considered, by some, to be promising, however (Hautarzt. 2009;60:795-801). And, in fact, Guéniche et al. have found that the topical application of Vitreoscilla filiformis demonstrated efficacy against seborrheic dermatitis and AD (J. Eur. Acad. Dermatol. Venereol. 2008;22:1014-5; Eur. J. Dermatol. 2006;16:380-4).
Conclusion
While still controversial, the findings of probiotics’ effects in the treatment of atopic dermatitis remain compelling. Even more interesting, though, is the current work that suggests additional potential applications of probiotics in the dermatologic armamentarium. The work is in its early stages, but results warrant additional research, at the very least, if not cause for optimism over the prospect of more supportive evidence.
Dr. Baumann is in private practice in Miami Beach. She did not disclose any conflicts of interest.