Background: Numerous novel medications are being developed to treat moderate to severe atopic dermatitis (AD), notably biologics and Janus kinase inhibitors (JAKis). However, the exact guideline for the first determination of which medication has not been established yet. This study was conducted to identify patients who would show favorable clinical results from using JAKis. Methods: Based on the degree of improvement in EASI at 16 weeks, 43 patients were divided into three groups: Group 1 (EASI-90), Group 2 (EASI-75), and Group 3 (EASI-50). Results: Compared to Group 1 and Group 2, Group 3 exhibited a significantly higher rate of multiple positive results in MAST (p-value = 0.005, p-value = 0.004), a greater proportion of individuals with higher IgE levels exceeding 1000 (p-value = 0.003, p-value = 0.027), and the presence of allergic comorbidities (p-value = 0.049, p-value = 0.026). However, baseline laboratory test results, such as eosinophil counts, LDH, and so on, showed no significant differences among the three groups. Conclusions: JAKis might provide prompt clinical improvement, especially in patients with relatively low serum Ig E levels who do not have multiple allergen positivities and allergic comorbidities.