## 4 Discussion  
The SC of the skin primarily acts as an external barrier for the human body and the lipid barrier of the SC plays an important role in this context. Two of its functions are to prevent excessive water loss through the skin and prevent the entry of harmful substances into the body [36]. Therefore, defects in the lipid barrier can facilitate sensitization by increasing antigen permeability, which can lead to AD [4; 37; 36; 38]. FLG is one of the various components of SC and it functions in the aggregation of keratin filaments. FLG is being studied as a central component in the pathogenesis of AD and other allergic diseases [39; 40], starting with a study in 1996 [41], which showed a decrease in the expression of FLG in the skin of patients with AD. In traditional Korean medicine, Hataedock treatment is used to remove \"fetal heat\" [12] which is a cause of AD. 3 Hb is the core ingredient used in the Hataedock treatment. Previous studies [10; 11; 12; 13; 14; 15; 16] have shown the effectiveness of alleviating AD by maintaining the lipid barrier through the use of 3 Hb extract. Therefore, we assumed that the use of the 3 Hb  
Figure 6: The regulation of the skin micro-environment for defense using Three Herb (3 Hb) extract. The expression of claud, cathelicidin, TLR, NHE (light brown particles indicated by arrows) was significantly lower in 3 HbT compared to PEAT and LBE (immunohistochemistry; bar size, 50 μm). The data of image analysis for a positive reaction showed the same results. 3 Hb, _Rhizome_ of _Coptis chinensis_, _Rhizome_ of _Glycyrrhiza valensis_, and fermented _Semen of Glycine max_; Ctrl, the normal group; LBE, lipid barrier elimination group; 3 HbT, 3 Hb treated group after lipid barrier elimination; Cathe, cathelicidin; TLR, toll-like receptor; NHE, sodium hydrogen antiporter; Epi, epidermis; * \(p\) < 0.05 compared to LBE; # \(p\) < 0.05 compared to PEAT. extract would work as a \"proactive therapy\" that could be administered prophylactically prior to the presentation of symptoms, and which could aid in suppressing a subsequent series of processes, by maintaining the lipid barrier through the recovery of FLG. Based on these assumptions, we used the lipid barrier-eliminated Balb/C mice to check the effectiveness of FLG and study its effect on general skin features, inflammatory reactions, the Th2 differentiation process, and skin microenvironment. We also used HPLC for quality control and the identification of the components of the 3 Hb extract. A decreased positive reaction and expression of FLG in LBE group indicates that damage to the lipid barrier causes reduced expression of FLG in the skin. As expected, the positive reaction and expression of FLG in 3 HbT mice showed a substantial increase compared to that in the PEAT and LBE groups. The 3 Hb extract has an effect on the recovery of FLG, which is superior to that of PEA. FLG has important roles in skin acidification and hydration and exhibits antimicrobial functions [34]. Therefore, FLG deficiency negatively affects the formation of keratinocytes, decreases adhesion between keratinocytes, and increases TEWL, leading to a decrease in the overall skin barrier function. This increases the probability of sensitization and allergic reactions due to increased penetration of external allergens. In addition, the pH of the SC increases due to a decrease in trans-UCA (a degradation product of FLG), and a decrease in the contents of amino acids and pyrrolidone carboxylic acid causes dryness of the skin [26]. In this study, the pH and TEWL in the skin were significantly decreased in the 3 HbT group compared to the LBE and PEAT groups. This suggests that the 3 Hb extract can restore FLG, resulting in an increase in trans-UCA and recovery of FLG function. A previous study [33] showed that TEWL can act as a predictable indicator of the occurrence of early childhood AD, thus inferring the effectiveness of 3 Hb extract administration as a proactive therapy for AD.