A red rash on the neck could be eczema-like dermatitis. Eczema-like dermatitis occurs mostly as a result of allergies or decreased immune function, as well as dietary factors. This rash usually appears as papules and papules on a large erythematous base, and may also be accompanied by varying degrees of exudation. In addition, it can also be prickly heat, especially after the summer season, which may lead to localized sweating in the neck, resulting in prickly heat. In addition, it may also be a fungal infection that causes a red rash. After a fungal infection, a local inflammatory reaction may occur, resulting in a red papule or herpetiform rash, which may be accompanied by scaling.