Viral infections are illnesses caused by a virus rather than bacteria or fungi. Many viral infections, especially those that tend to affect toddlers and children, can cause skin rashes. While they can look alarming, they usually aren’t cause for concern, and they disappear once the infection clears up.

Read on to learn more about the symptoms of a viral rash, including when you should see your doctor.

The characteristics of viral rashes can vary greatly. However, most look like splotchy red spots. These spots might come on suddenly or appear gradually over several days. They can also appear in a small section or cover multiple areas. For example, a measles-related rash starts on your cheeks before eventually spreading to your torso and limbs.

Viral rashes might also feel itchy or painful to the touch. The best way to identify a viral rash is to check for any symptoms of a viral infection, such as:

  • fever
  • chills
  • body aches
  • fatigue

Viral rashes are caused by either an immune response to the virus or damage to skin cells from the virus.

In the case of measles, for example, your immune system detects the virus as it travels through your bloodstream. Immune cells then release chemicals to destroy the virus. However, these chemicals also cause skin inflammation, resulting in a rash.

Shingles, on the other hand, involves a reactivation of chickenpox virus lying dormant in your nerves. When the virus reactivates, it travels down your nerves to your skin. As the virus replicates there, the shingles rash begins to form.

Other viral infections that can cause rashes include:

Viral rashes aren’t contagious but the viruses that cause them usually are. Some of the most contagious viral infections that cause a rash include:

  • measles
  • chickenpox
  • rubella

These infections are usually spread through respiratory droplets in the air or direct contact with nose or throat secretions. People with this kind of viral infection can be contagious before the rash appears. For example, people with rubella may be contagious for a full week before they develop a rash. They’ll usually continue to be contagious for another week after the rash appears.

Some other viral infections are spread by insects such as mosquitos, ticks, and fleas. Examples of these viruses include Zika virus and West Nile virus.

Viral infections often have to run their course. Unlike bacterial infections, they don’t respond to antibiotics, so treatment usually focuses on relieving symptoms.

You can try to speed up the healing process by drinking lots of fluids and allowing your body plenty of rest. If you have a fever or body aches, you can take medications such as acetaminophen (Tylenol) or nonsteroidal anti-inflammatories such as ibuprofen (Advil).

If you have an itchy viral rash, you can try applying a cool compress or calamine lotion to the affected area. Try to avoid scratching it if you can.

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For some viral infections, such as shingles, your doctor might prescribe an antiviral medication.

While it’s always a good idea to see your doctor when you notice a new rash, you should definitely make an appointment if you have a rash that:

  • lasts longer than a week, especially if it doesn’t seem to be improving
  • starts to blister
  • spreads rapidly or is all over your body
  • shows signs of redness, swelling, and oozing
  • is painful

Many viral infections can cause a skin rash. While the rash itself isn’t contagious, the underling viral infection often is. Most viral infections clear up on their own, but some may require antiviral medication. Contact your doctor if the rash doesn’t seem to be getting any better after a week.

You should also see your doctor if you have a rash and live in or have recently visited a tropical or subtropical climate. Illnesses spread by insects tend to be more common in these areas and may require antiviral medication.

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