## 2 Characteristics of Atopic Dermatitis: Types and Clinical Symptoms  
Recent studies suggest that atopic dermatitis, as a heterogeneous and multifactorial disease, can be classified into different types. Taking into account all the classifications that have been created to group patients with AD, clinical features and the results of biochemical markers can be indicated as common criteria [2; 12; 32]. These include clinical symptoms, the state of the epidermal barrier, the level of IgE immunoglobulin in the blood and demographics such as age, gender or ethnicity [2; 12; 32]. The first such diagnostic criteria for AD were published by Hungarian dermatologist [PERSON] [5]. [PERSON] and [PERSON]'s criteria, which were published in 1980, are still widely used for diagnostic purposes [33]. They were developed based on clinical experience and the consensus of experienced dermatologists, but without objective clinical validation [34]. To diagnose atopic dermatitis in a patient, he or she should meet three of the four so-called \"major\" (main) criteria and three of the twenty-three \"minor\" (secondary) criteria [33] (Table 2). \begin{table}
\begin{tabular}{l l} \hline \hline \multicolumn{1}{c}{**“GREATER” CRITERIA**} & **“LESSFR” CRITERIA** \\ \hline \hline \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \hline \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \hline \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \hline \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \hline \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ \end{tabular}
\end{table} 
Table 2: Diagnostic criteria of atopic dermatitis according to [PERSON] and [PERSON] based on [35]. It is noteworthy that only seven of the twenty-three minor criteria are due to immunological disorders, supporting the statement that atopic dermatitis is a multifactorial disease [33]. Currently, the most widely used scale that assesses both objective and subjective symptoms of atopic dermatitis is the SCORing Atopic Dermatitis Index (SCORAD) [36]. It was developed by the European Task Force on Atopic Dermatitis (ETFAD) in 1993. The severity of skin lesions is assessed based on six criteria: erythema, edema, oozing or scabs, lichenization and dry skin (ranging from 0, i.e., no lesions, to 3, i.e., the most severe lesions) [36]. Subjective symptoms (severity of pruritus and sleep disturbance), on the other hand, are assessed on an analog scale (0 to 10). Based on the above criteria, atopic dermatitis is assessed as mild (less than 25 points), moderate (25-50 points) and severe (>50 points) [36; 37]. Numerous studies [36; 37; 38; 39] on the validation of the SCORAD scale have confirmed that it is a reliable method in both clinical trials and daily medical practice. The SCORAD scale is sensitive to changes, easy to interpret and has good reproducibility in both the examination and diagnosis of children and adults with different courses of atopic dermatitis [36; 37; 38; 39]. The classification distinguishes between external and internal subtypes of atopic dermatitis. The external subtype is characterized by high serum IgE levels and eosinophil. In addition, there is an increase in the filaggrin mutation rate in the skin of these patients. The external subtype of AD often coexists with other allergic diseases [32; 40]. In a study conducted by the authors [41], it was found that about 35% of children with moderate to severe atopic dermatitis also have another type of food allergy. In contrast, the intrinsic subtype of AD occurs with normal serum IgE levels. It is most common in women and has no atopic background [32; 40]. Another classification can be a division that distinguishes between acute and chronic subtypes of AD. We can group atopic dermatitis by ethnic difference [40]. Tests have been conducted that analyzed the Asian endotype of atopic dermatitis. They showed increased TH17 levels in the blood and severe eczematous skin lesions in Japanese atopic dermatitis patients.