Atopic dermatitis (AD) has traditionally been regarded as a skin disorder; however, accumulating clinical evidence suggests that it may represent a multi-organ disease involving the intestinal tract and cervical spine. This article reviews the authors’ long-term clinical experience and observations regarding the systemic involvement of AD, particularly in relation to Staphylococcus aureus colonization and superantigen-mediated inflammation. Previous studies have demonstrated a high prevalence of S. aureus on the skin of AD patients, elevated serum IgE levels, and positivity for antibodies against staphylococcal enterotoxins. The authors further investigated gastrointestinal and cervical spine abnormalities in AD patients through duodenal biopsy and cervical MRI examinations. Among 32 examined patients, 65.6% showed both duodenal and cervical spine abnormalities, suggesting significant extra-cutaneous involvement. In addition, the article presents a representative case of severe AD treated with standard therapy combined with topical povidone-iodine disinfection therapy. Marked clinical improvement was accompanied by substantial reductions in serum TARC, IgE, and anti-SEA antibody levels over time. These findings support the hypothesis that superantigens produced by S. aureus contribute not only to skin inflammation but also to systemic organ involvement in AD. The authors conclude that atopic dermatitis should be considered a multisystem disorder requiring comprehensive evaluation and management beyond the skin alone.