The inheritance of atopy was recognized early, though a clear mode of its transmission has not been defined. In a study of 372 AD patients, 59% had respiratory allergies and 73% reported a positive family history of atopy^[19]. In this cohort, the frequencies of asthma and allergic rhinitis in family members of those patients without personal respiratory allergy were quite high at 73% and 32%, respectively. Interestingly, the frequencies of AD in the families of AD patients, with or without personal respiratory allergy, were 34% and 27%, respectively, suggesting that the inheritance of AD was not strongly associated with AD itself but instead was closely associated with the atopic state, especially respiratory allergy. Another study on the familial aggregation of AD, allergic asthma and allergic rhinitis showed that familial aggregation was stronger between siblings than between parents and siblings. Also, a higher risk for AD was associated with maternal rather than …