A maculopapular rash is a skin condition characterized by the presence of both macules and papules on the skin. When a person's skin displays a maculopapular rash, it is usually red, and covered with many small bumps, not unlike sandpaper at times. This type of rash can have many causes, but it most often appears as a symptom of scarlet fever, measles, heat rash, and some hemorrhagic fevers. An allergic reaction to the antibiotic amoxicillin can also take on this appearance.
The two elements present in every maculopapular rash are macules and papules. Macules are areas of skin discoloration that are usually less than about half an inch (one cm) in diameter. They are neither elevated nor depressed, and can take on nearly any color. Macules themselves can have various causes, including certain skin diseases, but also including conditions, such as hyperpigmentation, that are in no way pathological.
Papules are small, round elevations of the skin that don't appear to contain any fluid. They also vary in color from pink or red, to purple, or even brown. Like macules, they usually present as a symptom of a skin disease. Heat rash is one of these diseases, and occurs primarily in hot, tropical climates due to the clogging of the sweat glands, and a subsequent bacterial infection. Heat rash is usually present only on a localized area, and is most common in infants and small children, because their sweat glands are less developed than those of adults.
Maculopapular rashes, which combine both of the above elements, are most often part of a serious or acute condition. Measles is among these, and apart from the rash, is characterized by a high fever, sometimes reaching 104 degrees Fahrenheit (40 degrees C). The measles rash develops some time after the fever, and can change colors from red to brown before eventually disappearing.
Scarlet fever is characterized in part by the appearance of a maculopapular rash, starting one to two days after the fever itself. Three to four days later, it fades, and the skin of the affected areas peels away, which is a process that sometimes takes weeks. Other ailments characterized by fevers also cause this condition. One of the more serious of these is Marburg hemorrhagic fever. The onset of symptoms in this case is very rapid, with the rash developing about five days later. Marburg hemorrhagic fever ends in the death of almost a quarter of all its victims.