Many viral infections can cause a rash in addition to other symptoms. Rashes are very common with viral infections, especially in young children. It is very important to make sure the rash is not part of a serious infection - eg, meningococcal infection which can be associated with meningitis. If you have any concerns then you should contact your GP immediately.
What is a viral rash?
The symptoms caused by viral infections can vary depending upon the virus. One of the symptoms that may occur is a rash. There are some well-known viral rashes. For example, the measles virus and the chickenpox virus cause characteristic rashes along with other symptoms. Sometimes a typical rash helps a doctor to diagnose which virus is causing an illness.
Many viruses can cause a rash in addition to other symptoms such as high temperature (fever) and cough. Many of these rashes are 'nonspecific'. This means the rash is not specific or characteristic enough to identify the virus that is causing the rash. The doctor cannot say which virus is the culprit, but can say that some virus is a likely cause of the rash.Rashes in children
The first thing to do when your child develops a rash is to reach for a tumbler. Run the glass over the rash to see whether it disappears under this mild pressure. If it doesn't, it's known as a non-blanching rash and can be a sign of serious infection.— Dr Tamara Bugembe, What to do when your child has a rash
Viral rashes vary in shape and size. However, they often appear as blotchy red spots. Commonly they affect most of your body. Sometimes they appear dramatically. For example, you may wake up in the morning to find yourself covered in a rash. It usually lasts only a few days. Sometimes the rash is slightly itchy. Usually the rash disappears without trace within a few days. There is a great variety of types.
1 in 6
People who will have a bout of hives in their lives.
Source: Hives Information Leaflet
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Are viral rashes serious?
The viral rash itself is not usually serious. However, it is very important to make sure the rash is not part of a serious infection - eg, meningococcal infection. Other signs suggestive of meningococcal infection in babies and young children include becoming floppy and unresponsive, unusual crying, being very sleepy and having a very high temperature (fever). The rash of meningococcal infection is usually purple or red spots that don't fade when put under pressure (for example, by pressing a clear glass against your skin).
Reproduced with permission from Meningitis Now
If you have any concerns then you should contact a doctor immediately.
What matters is whether other symptoms or problems occur. For example, the measles virus can cause a nasty illness with a chest infection, severe diarrhoea, etc, in addition to a rash. However, many viruses cause only minor symptoms - perhaps a mild fever or slight cough - but the rash may look quite dramatic. Sometimes the rash appears just as the other symptoms are improving.
Most viral infections causing a rash will do no harm to your developing baby. However, some may do. For example, the rubella (German measles) virus. It is therefore often best for pregnant women to avoid people who have an infectious rash. Also, if you are pregnant and develop a rash, it is advisable to see a doctor for advice.
The sudden appearance of a widespread blotchy rash is quite common. It is often due to a viral infection. It is the other symptoms that may be of more concern. If other symptoms are mild then there is usually little to worry about. It will usually go in a few days. There is no specific treatment for the rash itself. Treatment should be aimed at the other symptoms. For example, paracetamol can be used for a high temperature (fever).
Rashes that are itchy often respond to an antihistamine tablet which can be obtained from your doctor or a chemist. There are also various creams available which can work to alleviate itching.
Consult a doctor if you are concerned that a rash or other symptoms may be serious.
Further reading and references
Fever in under 5s: assessment and initial management; NICE Guidance (November 2019)
Viral skin infections; DermNet NZ
Viral rash in pregnancy; Public Health England