Unmasking multifactorial dermatitis: The case for comprehensive diagnostic guidelines in adult atopic dermatitis.

Eczematous dermatitis is a heterogeneous group of inflammatory skin disorders characterized by pruritus, erythema, and scaling. The most common subtype is atopic dermatitis (AD), which has a continuously rising prevalence, particularly within industrialized regions, e.g., the United States. Distinguishing AD from other dermatoses, particularly among adult patients with recalcitrant disease, can be challenging. Conditions such as allergic contact dermatitis may mimic or coexist with AD, which complicate both diagnosis and management. This diagnostic complexity has been unmasked with the introduction of targeted biologic therapies, including interleukin (IL) 4, IL-13, and IL-31 inhibitors, which have brought meaningful advances to the treatment landscape but also demands greater diagnostic precision. In this context, failure to identify overlapping or alternative conditions may delay optimal patient management or result in unnecessary therapeutic escalation to systemic agents, some of which have notable risk profiles. This review highlights the critical need for comprehensive diagnostic guidelines for the evaluation of adults with presumed AD, particularly those who exhibit an incomplete response to therapy. Diagnostic tools such as biopsies, cultures, laboratory studies, and expanded series patch testing have the potential to reveal underlying or comorbid conditions that fundamentally alter management strategies. With evidence that substantiates that a majority of patients with AD and with residual dermatitis on biologic therapy test positive for relevant contact allergen(s) on expanded series patch testing, the Clear, Patch, Avoid, and Treat strategy exemplifies a practical, stepwise framework for evaluating treatment-resistant eczematous dermatitis, which reinforces the clinical value of early diagnostic assessment and allergen avoidance. Establishing clear, evidence-based protocols is essential to support dermatologists and allergists in delivering individualized, high-quality care. In the absence of such guidelines, a methodical and comprehensive diagnostic approach remains the best tool to improve outcomes and reduce the burden of misdiagnosis in patients with complex or treatment-resistant dermatitis.