Causes and Risk Factors of Scarlet Fever

The term scarlet fever might sound scary to many people, but there is a common cause for this illness that isn't nearly as frightening as it may seem.

Although there are any number of reasons a person may develop a rash, only Group A streptococcus causes scarlet fever. Group A Streptococcus is a bacteria that commonly causes strep throat in school-age children and adults. It can also cause impetigo, which is a bacterial infection on the skin. Very rarely, some people with Group A strep infections may develop post-streptococcal glomerulonephritis—a kidney disease that occurs after strep throat, scarlet fever, or impetigo.

Scarlet fever is the term used when a person infected with Group A Streptococcus (most commonly strep throat) also develops a rash. The rash appears on the torso—more specifically, the chest and abdomen—and consists of fine, red bumps that appear similar to sandpaper. In fact, it is often referred to as a "sandpaper rash."

There are no known genetic risk factors that make a person more likely than others to get scarlet fever, but age and exposure to others with the illness are the known risk factors for getting it.

Contact and Exposure

Scarlet fever (and strep throat) are most common in children between the ages of 5 and 15. Teachers and caregivers of children in this age range are also more likely to get it—if you are frequently exposed to school-age children, your chances of getting scarlet fever are higher than they would be otherwise. However, it is usually not a serious illness when it is treated appropriately. 

Scarlet fever and strep throat are spread through contact with infected people. They are passed through respiratory droplets, shared when someone infected with the bacteria coughs or sneezes and another person breathes those droplets in. It is also passed through shared drinks and utensils that may have saliva from an infected person on them.

The CDC reports that it is possible, but rare, for Group A strep to be passed through food if it is handled improperly. It is not known to live on or be passed through handling of objects such as toys and hard surfaces.

Taking care to wash your hands, or use hand sanitizer if soap and water are not available, can reduce the chances that you will get scarlet fever if you are around someone that has it. Try to avoid contact with people that are known to have scarlet fever until they have been on antibiotics for 24 hours. Encourage children to wash their hands frequently and not share drinks or other items that they may put in their mouths.