Relationship between the average projected area of corneocytes and the onset age of atopic dermatitis in childhood

In childhood, atopic dermatitis typically begins around 2--6 months of age. It is thought that the skin barrier dysfunction as well as allergic disease is important in the mechanism of atopic dermatitis. However, there are few reports of the skin barrier function in childhood. So we examined the relationship between the longitudinal surveys of the skin barrier function through the average projected area of corneocytes (APAc) and clinical findings in children from 1 to 12 months. As a result of examinations, APAc of cheek and upper arm in 1-month-old children is the same as those in adults, and APAc of cheek and upper arm decreases by 6 months of age. These results suggest that the skin barrier function decreases before or after the onset age of atopic dermatitis during childhood. Moreover, we examined APAc of children aged 0–5 for 1 year in the same nursery. APAc of upper arm in atopic dermatitis or atopic disposition has a significant difference compared with that of the other subjects in December. Furthermore, it was shown that change of APAc in the children under medical treatment was correlated with clinical findings. In conclusion, it was thought that the APAc shown as the index of skin barrier dysfunction is associated with the onset age of atopic dermatitis in childhood.