L. rhamnosus is the most studied species of Lactobacillus (Petrova et al., 2021). The peptidoglycan of L. rhamnosus CRL1505 can regulate the immune function of human intestinal epithelial and dendritic cells (Salva et al., 2021). Early exposure to LGG in dogs with AD had long-term immune effects and significantly reduced allergen-specific IgE despite the lack of a clear clinical effect (Marsella, 2009; Marsella et al., 2012). In clinical trials, infants aged 0–2 years had a reduced incidence of atopic eczema when their mothers have been administered LGG during pregnancy (Kalliomäki et al., 2003). The preventive effect of LGG extended to 4 years (Kalliomäki et al., 2003). LGG may enhance the gut barrier function and promote immune response development in infants with AD (Nermes et al., 2011). In 2016, researchers observed that L. rhamnosus IDCC 3201 tyndallizate (RHT3201) had the potential to treat AD. The mast cell count and serum IgE concentration in axillary lymph node cells were decreased in RHT3201-fed NC/Nga mice compared with those in the control group (Lee et al., 2016). Another animal experiment concluded that heat-treated LGG could improve the symptoms of NC/Nga mice with AD (Sawada et al., 2007). In 2020, Jeong and colleagues (Jeong et al., 2020a) found that RHT3201 had a therapeutic effect on AD in children. L. rhamnosus GG (LGG) is a strain of L. rhamnosus that regulates gut flora and reduces conditional pathogenic bacteria (Chen et al., 2020b). When children with AD were supplemented with LGG, the clinical severity and quality of life improved (Carucci et al., 2022). Simultaneously, the use of topical steroids was reduced (Carucci et al., 2022).

L. rhamnosus decreases the concentrations of eosinophilic cationic protein, eosinophil count, IL-31 (Jeong et al., 2020a), and serum IgE (Tanaka et al., 2009; Lee et al., 2016); supports a better Th1/Th2 balance (Wickens et al., 2008); prevents pathogenesis caused by large molecules in the intestine; accelerates immune maturation (Nermes et al., 2011); stimulates peripheral blood cells to secrete IL-10 (Kalliomäki et al., 2003; Sawada et al., 2007); converts growth factor β (Kalliomäki et al., 2003), and upregulates the production of IFN-γ at the skin level (Tanaka et al., 2009). However, not all L. rhamnosus strains are equally effective. Wickens et al. (2012) studied the efficacy of L. rhamnosus HN001 and HN019 in atopic diseases and demonstrated that L. rhamnosus HN001 was more effective in improving AD than L. rhamnosus HN019 (Wickens et al., 2012). Moreover, the protective effect on eczema can persist two years when L. rhamnosus HN001 is administered to children with AD (Wickens et al., 2008). In addition, L. rhamnosus HN001 can prevent atopic sensitization in the long term (Wickens et al., 2013). Moreover, several studies have shown that the protective effect of LGG against AD requires further investigation. Two randomized controlled trials have shown that prenatal LGG treatment was not associated with a reduced risk of eczema (Boyle et al., 2008; Boyle et al., 2011). No clear causal relationship between the positive effects of LGG and infantile eczema has been reported (Fölster-Holst et al., 2006; Grüber et al., 2007; Kopp et al., 2008; Rose et al., 2010).

Some probiotics affect multiple immune pathways through different mechanisms and protect against the pathogenesis of eczema (Wickens et al., 2008). However, supplementation mothers with L. rhamnosus HN019, was not effective in preventing eczema in infants, indicating that L. rhamnosus HN019 is less likely to be passed on to infants through breast milk (indirect supplementation route) (Wickens et al., 2018). One of the reasons that prenatal LGG was not shown to prevent eczema in infants may be that the impact of prenatal probiotic therapy on fetal B cell development was not excluded (Boyle et al., 2008). Prenatal LGG intake may not directly contribute to the effects of postpartum breast milk regulation. It is possible that postpartum intake by nursing mothers can alter immunity and/or microbiota to benefit breast milk composition (Boyle et al., 2011). Probiotics are commonly added to dairy products (Grüber et al., 2007), which can also affect the efficacy of L. rhamnosus in AD. It is important to note that the number of participants who completed the study and the subgroups analyzed were insufficient. In addition, the complexity of human life makes it challenging to achieve homogeneity. In addition, eczema in early infancy can naturally improve, and more than 40% of patients with AD recover around the age of 3 years (Illi et al., 2004). Moreover, it is more difficult for clinical trials to recruit sufficient human participants than for animal studies to include a sufficient number of animals.

L. rhamnosus has been shown to be effective in the prevention and treatment of AD in both animal and clinical experiments. However, future research needs to continue to explore different strains of L. rhamnosus and use strains with excellent laboratory efficacy in clinical trials. Effective strains of L. rhamnosus can be passed on to the offspring from the mother, and subsequently, infants may potentially not develop AD.

L. acidophilus is a commercially significant probiotic isolated from the human gastrointestinal tract (Bull et al., 2013). Moreover, it is an important class of bioprotective agents (Anjum et al., 2014). Supplementation with L. acidophilus L-92 significantly reduced vascular permeability in diseased mice and attenuated the clinical symptoms of AD (Shah et al., 2010). The administration of L. acidophilus L-92 not only significantly attenuated AD symptoms in children (Torii et al., 2011), but also improved the symptoms in adults (Inoue et al., 2014). L. acidophilus triggers an anti-inflammatory response (Goh et al., 2021). L. acidophilus L-92 inhibited the inflammatory response dominated by Th2 cells by activating regulatory T (Treg) and Th1 cells (Yamamoto et al., 2016). L. acidophilus L-55 decreased the occurrence of anaphylactic dermatitis-like skin lesions in NC/Nga mice by decreasing serum total IgE levels (Sunada et al., 2008). However, the findings on several strains of L. acidophilus have been inconsistent. For example, there is no evidence that L. acidophilus NCFM can improve AD (Larsen et al., 2011). Supplementation with L. acidophilus LAVRI-A1 in children with allergies did not reduce the risk of dermatitis (Taylor et al., 2007; Prescott et al., 2008; Jensen et al., 2012), and the sensitization rate in the L. acidophilus LAVRI-A1 group was significantly higher than that in the control group (Taylor et al., 2007).

In early studies, L. acidophilus demonstrated good safety and efficacy in children with AD, and future studies in mothers are ongoing or are expected to begin soon. In addition, the time required to evaluate clinical outcomes is insufficient. The detailed interplay between the early microbial environment and the developing immune system remains largely unknown and requires further exploration. Overall, the findings suggest that not every strain of L. acidophilus has the potential to prevent or treat AD. The effect of L. acidophilus on the prevention of AD requires further study.

L. plantarum is a rod-shaped lactic acid-producing bacterium that is used in probiotics and silage production. L. plantarum has the potential to be a highly effective immunomodulatory probiotic in the human gut microbiome. In recent years, an increasing number of studies have shown the health benefits of L. plantarum. (Seddik et al., 2017). The extract of fermented blueberry black rice containing L. plantarum MG4221 had an effect similar to that of dexamethasone, but with fewer side effects; oral administration of FBBBR in NC/Nga mice reduced skin dryness, erythema, and scratch behavior (Hong et al., 2021a). L. plantarum NCIMB8826 can soothe the skin of mice with AD, strengthen the skin barrier, and alleviate scratching (Mariman et al., 2016). Supplementation with L. plantarum CJLP133 and IS-10506 has been shown to be beneficial for treating AD in children (Han et al., 2012; Kim et al., 2017; Prakoeswa et al., 2017). In addition, L. plantarum IS-10506 has an immunomodulatory effect and can effectively relieve AD symptoms in adults (Prakoeswa et al., 2022).

L. plantarum BF_15 can successfully colonize murine intestines by rebalancing intestinal microbiota (Zhang et al., 2020). The extract of fermented blueberry black rice containing L. plantarum MG4221 inhibited the production of serum IgE and Th2 cell-related cytokines, suggesting that fermented blueberry black rice may be an essential functional food in AD (Hong et al., 2021a). Additionally, oral administration of L. plantarum NCIMB8826 reduced the number of mast cells in the colon. Finally, Staphylococcus aureus infection is the main reason for the exacerbation of AD-like symptoms, but L. plantarum can alleviate AD-like symptoms by inhibiting Staphylococcus aureus (Kim et al., 2020b). Additionally, lipoteichoic acids isolated from L. plantarum and Staphylococcus aureus have shown anti-AD effects. Lipoteichoic acid combination therapy can alleviate AD by reducing the formation of membrane attack complexes and inhibiting Th1 reactions (Kim et al., 2019c). Notably, L. plantarum LM1004 not only regulates the host immune system and gut microbiota, but is also promising for the treatment of AD and obesity in humans (Kim et al., 2019a). Collectively, the preliminary evidence suggests L. plantarum is a potential therapeutic strategy. Moreover, it has an acceptable safety profile in adults. L. plantarum improves the symptoms of AD, although it is ineffective in preventing AD. Future research should focus on the preventive effects of L. plantarum on AD. L. plantarum is a promising Lactobacillus strain that can be further explored to improve treatment options and efficacy.

L. sakei was isolated from fermented meat, fish, and kimchi. L. sakei KDP is a potent antioxidant and antibacterial agent (Ghoneum and Abdulmalek, 2021). L. sakei 07, combined with Bifidobacterium bifidum B10, regulates immunity and the gut microbiota (Wang et al., 2019). Oral administration of live and inactivate (Kim et al., 2013; Rather et al., 2021) L. sakei probio65 can increase skin sebum content and improve the function of the skin barrier (Rather et al., 2021). L. sakei probio65 inhibits AD-like skin lesions and may serve as an influential novel anti-inflammatory medication that resolves AD symptoms in mice (Kim et al., 2013). In experimental dogs (Kim et al., 2015a) and mice (Park et al., 2008) with AD, orally administered L. sakei probio65 significantly reduced the disease severity index without clear side effects. Supplemental treatment with L. sakei KCTC 10755BP has the potential to alleviate the clinical severity of AD syndrome in children (Woo et al., 2010).

L. sakei WIKIM30 was isolated from kimchi and can significantly reduce AD-like skin lesions, regulate allergic Th2 responses, increase the relative abundance of intestinal bacteria positively correlated with Treg production, and has potential in AD treatment (Kwon et al., 2018). Current research shows that L. sakei can be anti-inflammatory and can protect the skin barrier. L. sakei has the potential to be used as a therapeutic supplement in AD. L. sakei originates from fermented foods, and direct intake of fermented foods may have the same effect. As mentioned above, both live and inactivated L. sakei have been shown to be effective. Fermented foods such as kimchi are popular and readily available, and patients can effortlessly benefit and achieve improvement of AD. Future research can further apply L. sakei in clinical practice and investigate its preventive effect on AD. In addition, the therapeutic effects of other strains of L. sakei can also be explored.

L. reuteri has been reported to occur naturally in the intestines of all vertebrates and mammals. L. reuteri induces neonatal IgA production (Mu et al., 2021). L. reuteri survives in the gastrointestinal tract of mammals and benefits host health (Engevik et al., 2021). L. reuteri NK33 can be used to improve gut dysbiosis (Han et al., 2020). L. reuteri strain, the Japan Collection of Microbiology 1112, significantly inhibited the expression of allergic lesions and thymus and activation-regulated chemokines at the site of lesions in NC/Nga mice (Kawahara et al., 2018). Prenatal and postnatal supplementation with L. reuteri Fn041 effectively prevented the fetus from developing AD, remodeled the intestinal ecology, and improved the immune function of Peyer’s patches (Qi et al., 2022; Zhou et al., 2022). L. reuteri Fn041 regulated the intestinal flora and significantly inhibited AD symptoms by regulating the systemic ratio of Th1 and Th2 cytokines in mice (Zhao et al., 2022). L. reuteri DYNDL22M62 attenuated AD symptoms by modulating gut bacteria in mice (Fang et al., 2022). Mothers and their babies supplied with L. reuteri ATCC 55730 had a lower prevalence of IgE-associated eczema at 2 years of age (Abrahamsson et al., 2007). However, in another clinical trial, L. reuteri ATCC 55730 did not improve clinical symptoms (Miniello et al., 2010). This may be because the small sample size. Alternatively, the duration of the experiment may have been too short. L. reuteri has been extracted from the gastrointestinal tract of all mammals, and future studies could explore the reasons for an absence of this L. and whether higher abundance of L. reuteri is beneficial. L. reuteri appears to have preventive and therapeutic effects in animals. Further clinical research on L. reuteri is required to explore the treatment and prevention of AD.

L. salivarius is a Lactobacillus species that occurs in the human gastrointestinal tract and oral mucosa. It produces bacteriocins, and is used as a probiotic. It modifies the gastrointestinal system to alleviate intestinal diseases and promote host health (Neville and O'Toole, 2010). L. salivarius is valuable for both animals and humans. L. salivarius can reduce pathogen colonization of the gastrointestinal tract of animals (Hong et al., 2021b). Administration of L. salivarius can prevent and treat a variety of chronic diseases in humans (Chaves et al., 2017), including AD, asthma, cancer, and bad breath (Drago et al., 2014). The combined administration of L. salivarius PM-A0006 and fructooligosaccharides exhibited a notable anti-AD effect compared with either therapy alone in the treatment of children with moderate-to-severe AD (Wu et al., 2012). L. salivarius LS01 can help manage AD in children and improve their quality of life; moreover, partial effect remains after termination of medication (Niccoli et al., 2014). L. salivarius LS01 actively improves the quality of life in adult patients with AD by regulating the balance of Th1/Th2 (Drago et al., 2011; Drago et al., 2012; Kim et al., 2014). Additionally, L. salivarius has shown efficacy in improving AD in existing studies. As the name suggests, L. salivarius is present in the oral cavity. The study of the oral environment is of great significance for increasing L. salivarius. The preventive effect of L. salivarius on AD requires further study. However, the long-term safety and persistence of L. salivarius remains to be studied. More potent subspecies of L. salivarius are yet to be discovered.

L. paracasei originates from the healthy human gastrointestinal tract and is widely distributed in food. L. paracasei has anti-inflammatory properties that can reduce antigenic pro-inflammatory responses. L. paracasei improves immune function by enhancing NK cell function and IFN-γ concentrations (Lee et al., 2017). In addition to a preventive effect on AD-like skin changes in mice L. paracasei KW3110 demonstrated inhibitory effects even when supplementation was started after symptoms have appeared (Wakabayashi et al., 2008). Supplementation with L. paracasei KW3110 can significantly reduce the development of AD-like skin lesions in mice, while regulating immunity (Wakabayashi et al., 2008). Oral supplementation with L. paracasei K71 can be used to treat dogs with AD (Ohshima-Terada et al., 2015). A diet with added K71 can be used as a complementary therapy for adult AD patients (Moroi et al., 2011). Moreover, L. paracasei NL41 reduced inflammation by improving the intestinal environment and maintaining intestinal integrity in rats (Zeng et al., 2021). Daily oral administration of L. plantarum HEAL9 and L. paracasei 8700 has been shown to regulate the peripheral immune response in children with celiac disease autoimmunity (Håkansson et al., 2019). L. paracasei KBL382 can significantly reduce AD-related lesions and epidermal thickening in mice by modulating the immune response and changing intestinal microbiota composition(Kim et al., 2020a).

Additionally, heat-killed L. paracasei CBA L74 has a minimal effect on steroid use, but its effect on reducing the severity of AD needs to be further studied (D'Auria et al., 2021). However, there is no evidence that L. paracasei GM-080 has a retention effect equivalent to that of glucocorticoids (Yan et al., 2019). This may be due to the inappropriate selection of L. paracasei strains, timing of administration, timing of exposure, and failure to achieve appropriate dosing levels. In conclusion, L. paracasei enhances NK cell function and IFN-γ concentrations to regulate immune mechanisms and achieve anti-inflammatory effects. Concurrently, L. paracasei can improve the intestinal environment and maintain intestinal homeostasis to achieve anti-inflammatory effects. The duration of L. paracasei administration does not require special emphasis, and intervention in patients with AD before and after the appearance of symptoms can achieve the desired effect. Hence, these studies might help clarify whether L. paracasei can improve intestinal barrier function and maintain immune system balance. Oral administration of L. paracasei can prevent and treat AD. However, more clinical experiments are needed to explore prevention of AD with the administration of L. paracasei.

L. casei is found in many fermented foods and coexists with gut microbiota. It is involved in housekeeping functions, metabolism, cell wall biogenesis, and environmental adaptation (Licandro-Seraut et al., 2014). L. casei CCFM1074 can balance gut microbiota and immune responses (Fan et al., 2021). L. casei regulates the host immune response (Aktas et al., 2016) and can be used to treat AD. During the Japanese cedar pollen season, NC/Nga mice orally administered L. casei Japan Collection of Microorganisms (JCM) 1134T combined with dextran experienced a possible effect on the prevention and treatment of allergic reactions (Ogawa et al., 2006). Furthermore, researchers screened an active ingredient, protein P14, from the L. casei extract, which specifically lowered IgE and IL-4 levels in AD-like NC/Nga mice, suggesting potential therapeutic effects in AD (Kim et al., 2015b). Similarly, the administration of L. casei DN–114001 to the diet of children with AD was beneficial to the increase in the count of intestinal flora and its maintenance for five months after the cessation of probiotics (Klewicka et al., 2011). L. casei DN—114001 can improve clinical symptoms in children with AD long term (Klewicka et al., 2011). Overall, these studies provide a good foundation for developing future therapeutic or preventive approaches using L. casei in individuals with AD. L. casei has an extended effect after stopping supplementation; therefore, the effect of permanent colonization of the intestine after regular supplementation should be studied. Few studies have been conducted on L. casei for the treatment of AD. More subspecies of L. casei are yet to be identified.

L. delbrueckii is one of the most economically valuable fermented Lactobacillus species. L. delbrueckii maintains and improves the intestinal barrier function by stimulating immune cells (Kobayashi et al., 2019). L. delbrueckii also improved intestinal integrity and immune responses in piglets (Chen et al., 2020a). L. delbrueckii subsp. bulgaricus may be involved in regulation of immune factor secretion in patients with AD (Sheikhi et al., 2017). IL-6 is a leading cause of dermatitis; whereas oral administration with L. delbrueckii subspecies bulgaricus OLL1073R-1 attenuated dermatitis by inhibiting the IL-6 response and restoring the elevation of serum amyloid levels in the NC/Nga mouse model of AD (Kano et al., 2013). In addition, oral supplementation with heat-treated L. delbrueckii R-037 can inhibit the rise of serum total IgE in allergic model mice, decrease inflammation, and alleviate AD; however, its effect on serum total IgE levels needs to be further studied (Watanabe et al., 2009). Studies in animal (mouse) models and have shown that L. delbrueckii plays a role in the management of AD. Experimental samples are easier to obtain in animal experiments than in clinical studies. However, only results of clinical studies that show the efficacy of L. delbrueckii will enable its widespread use in the management of patients with AD. In future, it will be necessary to further investigate the use of L. delbrueckii in patients with AD, including factors such as the time of supplementation, dosage, and strain activity. Moreover, the understanding of the preventive function of L. delbrueckii requires further experiments in both animals and humans.

L. fermentum is a gram-positive bacterium. It can improve the functionality and nutritional value of foods (Naghmouchi et al., 2020). L. fermentum can restore homeostasis of the intestinal microflora and regulate the immune response in mice (Rodríguez-Nogales et al., 2017). Mice were immunized with L. fermentum NWS29 and exposed to ovalbumin. L. fermentum NWS29 inhibited the expression of certain inflammatory factors to achieve an anti-inflammatory effect (Nawaz et al., 2015). Mice were inoculated with the Salmonella vaccine and L. fermentum PC2. When mice were challenged with live Salmonella typhimurium, L. fermentum enhanced mucosal and immune responses and played a protective role (Esvaran and Conway, 2012). L. fermentum KBL374 and KBL375 can modulate the innate immune response by improving intestinal barrier function and reducing leukocyte infiltration in mice (Jang et al., 2019). L. fermentum CJL-112 protected mice from the deadly influenza virus infection by stimulating macrophages, activating Th1 cells, and increasing immunoglobulin A production (Yeo et al., 2014). In a clinical trial, L. fermentum PCCTM strengthened Th1 IFN-γ responses and achieved clinical benefits in children with AD(Prescott et al., 2005).

L. fermentum MS15 inhibited exogenous IL-10 induced human β-defensin-2 and regulated the response to the inflammatory stimulus (Habil et al., 2014). In future, L. fermentum can be combined with other vaccines to enhance their protective effect (Esvaran and Conway, 2012). These different strains of L. fermentum have been shown to regulate immunity and may also have some effect in the prevention of AD. In future, more research is required to explore the potential of L. fermentum in the treatment of AD.

L. johnsonii is a probiotic that can be isolated from dairy products. Notably, L. johnsonii BS15 can regulate intestinal inflammation (Charlet et al., 2020; Xin et al., 2020a; Xin et al., 2020b; Wang et al., 2021). Oral administration of L. johnsonii NC553 can relieve the severity of AD and inhibit epidermal hyperplasia and infiltration of inflammatory cells into the skin (Inoue et al., 2007). Additionally, it relieves skin damage by inhibiting pro-inflammatory cytokines and CD86 (Inoue et al., 2007). Therefore, early administration of L. johnsonii NC553 in mice with allergies may help reduce AD exacerbations (Tanaka et al., 2008). L. johnsonii has been shown to improve intestinal inflammation in animal models. L. johnsonii is present in fermented dairy products, and it is worth investigating whether an effective dose can be achieved through daily yogurt intake in children. L. johnsonii can also ameliorate skin damage in mice. However, there have been few experiments related to the treatment of AD with L. johnsonii, and further research is needed to determine its effectiveness in the prevention and treatment of AD.

L. pentosus regulates the host immune system and plays an integral role in intestinal health (Ma et al., 2020). L. pentosus KF340 regulates systemic immunity and improves systemic inflammatory response (Kim et al., 2019b). L. pentosus S-PT84 may be involved in the modulation of immune mechanisms to alleviate clinical allergy symptoms (Majumder et al., 2020). Although administration of L. pentosus and placebo can improve symptoms, L. pentosus significantly improved the average subjective ratings evaluated using the SCORAD index for allergen-sensitizing AD (Ahn et al., 2020). L. pentosus KF340 reduced cell infiltration and serum IgE levels at the site of lesions in mice by inducing type 1 regulatory T cells (Tr1 cells) that produce IL-10 (Kim et al., 2019b). L. pentosus S-PT84 reduced the concentrations of histamine in the serum, mouse mast cell protease, total IgE, and IgG (Majumder et al., 2020). The detailed function of L. pentosus remains largely unknown and requires further investigation. L. pentosus has been shown to exert anti-inflammatory effects and benefit intestinal health. However, there is limited evidence on the efficacy of L. pentosus in the treatment and prevention of AD, and further research is needed.

L. brevis is a gram-positive, rod-shaped Lactobacillus that is frequently used as a starter culture in silage fermentation, sourdough, and lactic acid-fermented beer and wine. L. brevis is widely used in the fermentation industry. Orally administered L. brevis SBC8803 can significantly inhibit the production of IgE and severity of AD symptoms, and long-term use can inhibit AD development. However, it did not affect the production of cytokines produced by Th1 and Th2 (Segawa et al., 2008a). L. brevis NS1401, isolated from kimchi, stimulated immune cells to secrete Th1 or Th2 cytokines, balance Th1/Th2, and alleviate AD symptoms (Choi et al., 2017). L. brevis stabilizes the gut microbiota, prevents the growth of pathogenic bacteria, and reduces intestinal inflammation (Han et al., 2021). L. brevis can not only improve disease but also regulate immunity. In nine-week-old female BALB/c mice managed with L. brevis KB290 (3 × 109 CFU/g), cytotoxicity mediated by mouse splenocytes increased (Fukui et al., 2013). Similarly, the spleen cells of mice treated with L. brevis KCTC12777BP also expressed high levels of TNF-α. L. brevis 12777BP improves immunity in mice and prevents organisms from being invaded by pathogens (Jeong et al., 2020b). The supernatant of L. brevis BGZLS10-17 can be divided into two components: a GABA-containing and a GABA-free component (Bajić et al., 2020). The supernatant containing GABA relies on ATG5 autophagy to stimulate Foxp3+, IL-10, and transforming growth factor-β, CTLA4 and Sirp-α isoimmunoregulatory molecule expression (Bajić et al., 2020). The GABA-free supernatant can also regulate the immune response through other mechanisms (Bajić et al., 2020). Heated L. brevis KB290 accelerated the secretion of IL-8, induced ERK1/2 phosphorylation, increase p38MAPK phosphorylation, and enhanced the expression of IL-8 mRNA (Yakabe et al., 2013). Heated L. fermentans SBC8803 inhibited IgE production and histamine secretion (Segawa et al., 2008b). L. brevis regulates immunity through various mechanisms and has anti-inflammatory effects. Unfortunately, the prevention and treatment of AD by L. brevis remain unclear. L. brevis may be an innate probiotic to inhibit AD development, and is a promising Lactobacillus strain that requires further research.