A common cause of red cheeks in toddlers is a viral infection known as slapped cheek syndrome, or fifth disease, according to Boots WebMD. The illness begins with the sudden appearance of redness on the child's cheeks. Parvovirus 19 is the cause of this illness, which is typically mild in children. When an infected person coughs or sneezes, droplets containing the virus spread and can infect others. By the time the rash appears, the child is usually no longer contagious.
Other symptoms of fifth disease in children include fever and a rash on the arms and legs. The rash on the arms and legs may have a lacy appearance and can cause itching. Parents of a child with exposure to fifth disease should seek medical attention if their child has sickle cell anemia or another medical condition that causes an impaired immune system, advises Boots WebMD. Other reasons for the child to see a doctor are if the rash lasts longer than five weeks, turns purple, causes pain or blisters, or if the child seems very ill.
Since the disease is typically very mild, treatment is unnecessary for most children, says Boots WebMD. If the rash causes uncomfortable itching, an antihistamine may be helpful. For pain relief, over-the-counter medicine such as ibuprofen is usually adequate.