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Dysregulated gut microbiota is increasingly recognized as a major contributor to allergic diseases and their progression. A key clinical manifestation of this progression is the atopic march, in which atopic dermatitis (AD) precedes the development of allergic airway disease. Although prebiotics and probiotics individually improve AD symptoms, their combined use as synbiotics, especially with regard to preventing the progression from cutaneous inflammation to airway hypersensitivity, has not been clearly established. In this study, we assessed the biological activity of a synbiotic composed of fructo-oligosaccharides (FOS) and Lactococcus lactis LB1022 in an ovalbumin (OVA)-induced murine model of AD and asthma-like inflammation. Female BALB/c mice were treated for eight weeks with FOS, L. lactis LB1022, or their combination following OVA sensitization. The synbiotic formulation produced the strongest protective effects, markedly reducing AD-like skin pathology, suppressing airway inflammatory cell influx, and lowering Th2-skewed cytokine responses. These protective effects were further supported by significant reductions in serum IgE and Th2-associated IgG1 levels. Synbiotic treatment also enriched multiple short-chain fatty acid (SCFA)-producing taxa, including Lactobacillus and Bifidobacterium species, resulting in increased fecal SCFA concentrations that were closely associated with improvements in systemic and mucosal immunity. These results demonstrate that the FOS-L. lactis LB1022 synbiotic mitigates both epidermal and respiratory allergic inflammation through coordinated regulation of the microbiota-gut-skin-lung axis. The findings highlight a promising dietary approach for reducing the risk of progression along the atopic march and address an important gap in current allergy-related microbiome research.