A 14-year-old girl with acute myocarditis, transient eosinophilia, and hyper-IgE-emia associated with atopic dermatitis is described. The patient was admitted because of severe heart failure and shock, and severe atopic dermatitis was seen. Blood examinations showed moderate eosinophilia (1917/mm³) and hyper-IgE-emia (830 IU/ml). The response to treatment with dopamine was excellent, and the congestive heart failure was gradually ameliorated, followed by improvement in her atopic dermatitis. In addition, rapid improvement in eosinophilia and hyper-IgE-emia was observed. Histopathological examination of the right ventricular myocardium obtained by endomyocardial biopsy showed mild interstitial fibrosis and mild infiltrations of inflammatory cells, indicating myocarditis. We speculated that the transient eosinophilia and hyper-IgE-emia in the present case indicated that an allergen induced strong allergic reactions, including type 1 allergy, and caused both acute myocarditis and deterioration of the atopic dermatitis; specifically noteworthy is that the patient's disease rapidly improved without corticosteroid treatment.