RC), Zambia (Reference number TRC/ERC/04/10/2013). Consent to participate was not applicable in this study.


Introduction {#Sec1}
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In Japan, as in most developed countries, the prevalence of allergy, including atopic dermatitis (AD), food allergy (FA), asthma, and allergic rhinitis, among infants has increased in recent years and is a serious health problem \[[@CR1]\]. The "allergic march," which was first proposed by Minoru Baba, and refers to the chain reaction of allergies in people predisposed to atopic dermatitis \[[@CR2], [@CR3]\], has attracted a great deal of attention in recent years, and it has been suggested that preventative measures during the neonatal and early infancy period could be effective against this condition.

To date, extensive research has been conducted on the risk factors for, and preventative measures against, allergy during infancy. In addition, evidence supporting the efficacy of several of these preventative measures has accumulated. For example, in 2008, Lack hypothesized that sensitization to allergens occurs through environmental exposure to allergens through the skin and that consumption of food allergens induces oral tolerance (dual-allergen-exposure hypothesis \[[@CR4], [@CR5]\]), and proposed a new allergy-prevention strategy based on the maintenance of skin-barrier function. To verify the dual-allergen-exposure hypothesis, randomized clinical trials (RCTs) of the effects of a moisturizer were conducted, and its efficacy in AD patients was demonstrated \[[@CR6]--[@CR8]\]. Lowe et al. (2016) \[[@CR9]\] performed a meta-analysis and showed that a moisturizer can statistically significantly prevent infantile AD when used in the neonatal period, and that the onset of AD is associated with sensitization to egg-white antigen. On the other hand, this analysis suggested that the efficacy of moisturizer alone used from the neonatal period is poor because it cannot prevent sensitization to food allergens.

In addition to the dual-allergen-exposure hypothesis, some studies