Exanthem means skin rash or eruptions. Viral exanthems are skin rashes that develops in response to an infection from a virus. Viral exanthems are common in children. They usually appear abruptly and are preceded by fever, cough and malaise. There is a relationship between the onset of fever and the timing of appearance of rash that helps to identify the causes of viral exanthems. Usually viral exanthems are self limiting and disappear in few days . However these rashes should be evaluated to rule out other serious diseases like meningococcal infection, scarlet fever or Kawasaki disease.

Causes

Many viral infections can cause skin rashes. Common viral infections are:

• Measles (Rubeola):  The disease is also called 10 days measles. The rash first appears on face, particularly behind the ears, then spreads to chest, abdomen, arms and legs. The rash is red and raised and granular. It appears on the fourth day of fever and lasts for 4-7 days.  It takes 6-12 days for a child to develop symptoms after getting exposed to the virus. But the child may transmit the virus to others  even before (1-2 days) the onset of symptoms and 3-4 days after development of rashes. 
• Chicken pox: The rash starts as a red flat rash that soon become raised and later becomes fluid filled that ruptures and forms crusts before healing completely. Lesions at different stage are seen as new rashes continue to form for several days. It start on the trunk and spreads to limbs.  Appears on the first day of fever and lasts for 4-10 days. It may take 10-12 days for a child to develop symptoms after exposure. They are contagious 1-2 days before onset of rash until the rash crusts.
• Rubella: Also called German measles. The rash and disease is usually mild and transient. The rash starts from face or neck and then to trunk and limbs.  It is pink or light red in color. Major health concern from Rubella is in pregnant women. If a pregnant woman acquires Rubella in pregnancy it can cause significant damage to the fetus. It takes 2-3 weeks for a child to develop symptoms after getting exposed to Rubella. They are contagious 7 days before the onset of the rash to 14 days after the rash disappears.
• Erythema infectiosum (Fifth disease):  The rashes begin with the classic slapped-cheek appearance. Bright red raised rashes appear abruptly over the cheeks, sparing area around the nose, mouth and eyes. Later on, red rashes spread to arms and trunk which fades into a lace like reticular pattern. Up to two weeks may elapse before a child exposed to the virus develops any symptoms. A child can transmit virus before onset of rash and up to 20 percent may not have any symptoms and still transmit the virus.
• Roseola: A pink rash, with either flat or raised lesions, starts to appear on the trunk and then spreads to the face, arms and legs. This disease causes very high fever and a infected child is at risk of developing seizures. The rash appears as fever subsides.

Rashes may occur with other viral infections, such as  Epstein-Barr virus, Cytomegalovirus, echoviruses and coxsackieviruses.

Symptoms

Before rashes appear, a prodrome of symptoms are seen in all viral exanthems. The prodrome symptoms include fever, cough, headache, malaise, abdominal pain, decreased appetite, muscle aches, joint pain, runny nose, swollen neck glands or eyelids.  The duration and intensity of symptoms depend on different virus and in different individuals. As the disease progresses, these symptoms begin to subside or new symptoms of complication begin to appear.

Diagnosis

Diagnosis is made on the basis of evolution symptoms, timing and distribution of the rashes. Many exanthema have distinct patterns of rashes and prodromal (pre-rash) symptoms allowing to make a clinical diagnosis. However, the rashes may be nonspecific in some cases and diagnosis can only be confirmed with blood tests or isolation of viruses.

Treatment

There is no specific treatment for viral exanthema and the rashes usually resolve in a week or two. Treatment  is usually symptomatic and supportive. Still viral exanthemas (rashes) require clinical care by a physician as it needs to be monitored for appearance of any complications and for specific advice about prevention of transmission to other people. Some serious bacterial infections can also produce rashes, so the doctor needs to evaluate and make sure that you get appropriate diagnosis and treatment.

Symptomatic treatment includes paracetamol/acetaminophen for fever, skin moisturiser for itching.  Aspirin should be avoided for treatment of fever due to the risk of complication known as Reye’s syndrome in some children. In cases of measles, large doses of Vitamin A is given to treat possible complications in the eyes and to help you prevent acquiring secondary bacterial infection.

Prevention

Vaccinations against  measles, mumps, rubella and chickenpox  is the most important aspect of prevention and management of viral exanthems. Prevention of spread of infection is another important measure in prevention.  Children should not attend school or daycare for a period mentioned above depending on the disease type and state.