Skin care behavior consists of a body wash and emollient application. Western guidelines of AD advice patients not to use soap for a body wash [28, 30] since the pH of soap is alkaline which neutralizes skin pH and increases protease activity on the corneo-desmosome resulting in acceleration of epidermal barrier destruction [31], and limited use of nonsoap cleansers (that are neutral to low pH, hypoallergenic, and fragrance-free) is recommended [30].

Bathing system in Japan is different from that in the other countries. Typical way of Japanese bathing is composed of a body wash with bubbling soap at outside space of bathtub, washing away all bubbled soap from the body thoroughly with plenty of warm water before bathing, and soaking the cleared body in the warm water in the bathtub (bathing). Japanese way of bathing needs plenty of water to wash a body, and soap does not usually remain on the body surface.

Therefore, many Japanese patients do not mind using soap even if its pH is alkaline, and soap does not seem to damage their skin barrier as long as it is washed away thoroughly with plenty of warm water. Although this bathing way is effective to prevent infantile seborrheic eczema, babies are susceptible to dry skin if not applied with emollient after bathing, even in high humid climate in Japan. Many participants in the Japanese RCT for the prevention of AD washed their bodies with soap.

Recent epidemiological studies support that AD is one of the strong risk factors for the onset of food allergy and other allergic diseases such as bronchial asthma and allergic rhinitis [32–37]. And basic cutaneous researches have been revealing complex mechanisms of epidermal sensitization to allergens [38–42]. Treatment with proactive therapy and skin care was routinely instructed for childhood AD patients in the hospital the author have been working.

A case-control study showed that food allergen-specific IgE levels of AD patients proactively treated for 2 years significantly decreased than those of patients reactively treated [43]. An RCT carried out for prevention of hen’s egg allergy with early heated egg administration revealed that early intake of small doses of egg was effective for prevention of egg allergy but the two infants who failed to be prevented were not well controlled in their eczema [10]. Another RCT which compared proactive therapy with reactive therapy showed that proactively treated patients’ house dust mite-specific IgE remains low, while those of reactively treated patients significantly increased [44]. Post hoc analysis of the Japanese study of preventive RCT revealed that even congenitally vulnerable infants with high transepidermal water loss from birth could be protected from the onset of AD by skin care treatment with emollients carried out from first week of life [45]. A recent birth cohort study revealed that the earlier eczema emerges the higher risk of food allergy follows [46].

Those findings suggest that keeping skin clear with attentive skin care treatment might be protective against food allergy and the progression of atopic march in genetically high-risk children. In the future, large-scale intervention studies for longer period and prospective observational studies are expected to show the effectiveness of long-term skin care treatment with emollients on the onset of eczema and early intervention of eczema on prognosis of AD and other allergic diseases.