The classification of the severity of AD prepared by the Atopic Dermatitis Severity Classification-Reviewing Committee of the JDA is available for clinical studies because its statistical reliability and usefulness have been verified (Fig. 20.1) [2, 9]. For the severity classification, three elements of eruption (erythema/acute papules, exudation/crusts, and chronic papules/nodules/lichenification) are evaluated in the most severely affected part of each of the five body sites (head/neck, anterior trunk, posterior trunk, upper limbs, and lower limbs). The areas of eruption on the five body sites are also evaluated, and both scores are totalized (Fig. 20.1) (maximum score, 60). As a simple method reviewed by this committee, a method to divide the whole body into the same five sites and calculate the sum of the global assessment scores of these sites is also presented (Fig. 20.2) (maximum score, 20) [2, 10].

In addition, as another simple method, the severity index has also been proposed by the Research Group of the Ministry of Health, Labour and Welfare (Table 20.2) [11]. Internationally, the Severity Scoring of Atopic Dermatitis (SCORAD) (maximum score, 103) [12] established by the European Task Force on Atopic Dermatitis or the Eczema Area and Severity Index (EASI) (maximum score, 72) [13] in the USA is widely used.

As a severity classification considering the clinical course, the system of grading of the severity of AD published by Rajka and Langeland is frequently used [14]. Additionally, in the abovementioned ISAAC questionnaire, the question “In the last 12 months, how often, on average, have you (has your child) been kept awake at night by this itchy rash?” diagnoses patients as severe when they answer “1 or more nights per week” [7].

The visual analogue scale (VAS) is useful for evaluating pruritus [15]. In this scale, 1 point is marked on a 10-cm axis in accordance with the degree of pruritus, and the distance (mm) from the left end to the marked point is evaluated as the pruritus scale score, regarding the left end “no itch” as zero and the right end “the worst imaginable itch” as 100. As described in SCORAD (evaluated by the scale of 0–10 in SCORAD), VAS can also be used for sleep loss.

The Skindex-16 and Dermatology Life Quality Index (DLQI) have been statistically analyzed [16, 17]. Their Japanese versions were published and have been applied to the treatment of various skin diseases including AD [18, 19].

The primary treatment, application of topical corticosteroid, should be determined based on “the severity of each eruption” (Tables 20.3 and 20.4) [20]. Briefly, potent topical therapy is selected to treat severe eruption even when its extent is narrow. However, it is not required for patients with mild eruption even when its area is extensive. Therefore, “the severity of each eruption” is the most important factor to consider when selecting topical therapy, and a severity assessment must be performed by physicians with dermatological skills in order to evaluate severity and predict the treatment response.