Eczema herpeticum is a rare, painful skin rash usually caused by the herpes simplex virus (HSV). HSV-1 causes cold sores and can be transmitted through skin-to-skin contact.

Eczema herpeticum (EH) was initially called Kaposi varicelliform eruption after the doctor who first described it and thought the eruption looked like chickenpox.

EH most commonly affects infants and young children who have eczema or other inflammatory skin conditions. It can also affect adults.

Antiviral drugs treat EH. It can become severe and life threatening if not treated quickly.

The viral infection is contagious. If you have EH, be careful not to transmit it to other people who have eczema or compromised immune systems.

A 2023 analysis suggests the condition is becoming more prevalent and that people who had it once are more likely to get it again.

Keep reading to learn how to identify it, what causes it, and more.

The EH rash usually affects the face and neck, but it can occur on any area of the body, including skin that’s unaffected by eczema.

EH typically starts suddenly with clusters of small, fluid-filled blisters that are painful and itchy. The blisters all look alike and can be red, purplish, or black. The rash can spread to new sites for up to 7 to 10 days after the first outbreak.

The blisters ooze pus when they break open, and then the lesions crust over. The EH rash heals in 2 to 6 weeks. It can leave scars.

Other symptoms may include:

  • high fever
  • chills
  • swollen lymph glands
  • general unwell feeling

HSV-1 most often causes EH. HSV-2, the herpes simplex virus that leads to genital herpes, can also cause EH. EH usually erupts several days to more than a week after contact with a person who has HSV.

Some people with eczema can have ordinary cold sores that don’t spread. It’s not known exactly why others with eczema develop a more widespread EH infection, but the reason likely involves your immune system and the severity of your eczema.

Children with eczema are the most common group to have EH. Only a small percentage of children and others with eczema develop EH. People with severe or untreated eczema are more likely to be affected.

Eczema damages the outer layer of your skin, leaving it dry, sensitive, and more vulnerable to infection. Other possible risk factors are a lack of antiviral proteins and a lack of cells that promote antivirus immune responses.

Research from 2020 shows that people with EH had significantly earlier onset of eczema and significantly higher levels of the antibodies produced by their immune system to combat allergies.

Other risk factors include:

  • damaged skin resulting from other skin diseases or burns
  • certain prescription skin creams, such as tacrolimus (Prograf), that affect the skin’s immune system
  • exposure in a hot tub or bath

A doctor can likely diagnose EH by its appearance, but they may want to confirm the diagnosis. This is because EH can resemble some bacterial infections, like impetigo. It also can look like a severe flare-up of eczema or other skin issues.

Your doctor will probably have you take systemic antiviral drugs immediately if they think you have EH. Because EH can have serious complications, a doctor likely won’t wait for tests to confirm the presence of the virus.

A doctor can confirm an EH diagnosis by taking a smear of a blister to check for the virus. Several tests are available to identify the virus, including:

  • culturing the sample
  • identifying antibodies to the virus
  • examining it under a microscope

It’s also possible to have a secondary bacterial infection, which will also be identified for proper treatment.

If left untreated — or not treated soon enough — EH can lead to blindness (though this is rare) and other complications. If the lesions are near your eyes, your doctor will refer you to a specialist for evaluation. HSV can cause an eye infection, damaging the cornea.

Doctors routinely check people with eczema for signs of EH because of its potential seriousness. It’s usually considered an emergency, and quick diagnosis and treatment are essential.

A doctor will prescribe an antiviral drug, such as acyclovir (Zovirax) or valacyclovir (Valtrex), to be taken for 10 to 14 days until the EH lesions heal. If you’re too ill to take drugs by mouth, your doctor may prescribe intravenous antivirals.

Some severe cases may require hospitalization.

If you also have a bacterial infection with EH, your doctor will prescribe antibiotics.

Antiviral drugs will stop the EH outbreak, but the symptoms can come back again. Its return is usually milder after the first episode.

Getting treatment as soon as possible for EH can reduce your risk of complications. Antiviral drugs typically clear the EH rash within a couple of weeks. EH can recur, but recurrences aren’t as common. When it does come back, it’s usually milder.

If you have eczema, you can prevent EH by avoiding contact with someone who has a cold sore. Also avoid using anything that has touched the mouth of someone with a cold sore, such as a drinking glass, eating utensils, or lipstick.