Eczema herpeticum is a chronic dermatosis with erosive and ulcerative lesions of the skin in children of a predominantly young age. The clinical case presented in this article shows the severe course of herpesvirus infection combined with atopic dermatitis in a 5-month infant. A rash in the form of vesicles and pustules throughout the body with a predominant localisation on the skin of the face, the scalp, neck, and chest was found in the course of the examination of the child. Influence of infections on the course of allergic processes is an ambiguous and complicated issue. It has been proved that an infection can contribute to the development of allergies and exacerbate the course of already existing allergic inflammation. In recent years, an increasing number of studies have shown the preventive effect of infection on the development of allergic pathology in children, especially during the first years of life.