Miliaria (/ˌmɪl.iˈɛər.i.ə/; also called "sweat rash", "heat rash" or "prickly heat") is a skin disease marked by small and itchy rashes. Miliaria is a common ailment in hot and humid conditions, such as in the tropics and during the summer season. Although it affects people of all ages, it is especially common in children and infants due to their underdeveloped sweat glands.