Eczema herpeticum (EH) is a serious, rapidly spreading viral skin infection that develops almost exclusively in individuals with pre-existing skin conditions, most commonly atopic eczema. This infection is contagious and poses a significant risk, particularly to vulnerable populations. EH is considered a dermatological emergency because it can cause severe systemic illness, including high fever and organ involvement.
What Causes Eczema Herpeticum and How It Spreads
Eczema herpeticum is overwhelmingly caused by the Herpes Simplex Virus (HSV), typically HSV-1, the same virus responsible for common cold sores. HSV-2 can also be the cause. The infection occurs when the virus spreads widely across the skin rather than remaining localized. The virus is acquired through direct contact with active lesions, blister fluid, or saliva from someone with an active cold sore or EH outbreak.
Individuals with eczema are susceptible because their underlying condition compromises the skin barrier’s integrity. The skin, which normally acts as a shield against pathogens, has microscopic breaks and inflammation in eczema, allowing the herpes virus to bypass defenses easily. Once the virus gains entry, it rapidly spreads across the damaged skin surface. Infectious viral particles are concentrated within the fluid of the blisters that characterize the EH rash.
Determining the End of the Contagious Period
The duration of contagiousness is determined by the physical state of the skin lesions, not a set number of days. The infection is contagious from the first appearance of blisters until the last lesion has fully crusted and dried. This period of infectivity typically lasts for the entire active phase of the rash, usually ranging from one to two weeks, or longer if treatment is delayed.
The blisters initially contain clear, fluid-filled material packed with active virus particles, making them highly infectious upon rupture. As the body fights the infection, these blisters rupture, weep, and eventually begin crusting. Once a lesion is completely dry and has formed a hard, dark crust, it is no longer shedding live virus onto the skin surface.
The risk of transmission is highest during the weeping, fluid-filled stage, as contact with active blister fluid spreads the virus. Although overall skin healing can take two to six weeks, the patient is considered safe for normal contact only after every spot has transitioned into a dry scab. The presence of even a single moist or weeping lesion indicates the person is still shedding the virus and remains highly contagious.
Accelerating Recovery and Preventing Transmission
The most effective way to shorten the contagious window is through prompt medical treatment with antiviral medication. Systemic antiviral drugs, such as acyclovir or valacyclovir, inhibit the virus’s ability to replicate, speeding up the healing process and reducing the duration of viral shedding. Treatment should be initiated immediately upon suspicion of EH, often before laboratory confirmation, to minimize the spread and prevent severe complications.
Strict hygiene and isolation measures are necessary to prevent the transmission of the virus to others. The infected individual must practice meticulous hand hygiene, especially after touching the lesions, and should avoid all direct skin-to-skin contact. Towels, washcloths, and linens used by the patient should be kept separate and washed frequently to avoid indirect transfer of the virus.
For the duration of the active infection, individuals with EH should avoid contact with high-risk groups, including newborns, young children, pregnant women, and anyone with a compromised immune system. Infected children must be kept home from school or daycare until a healthcare provider confirms that all lesions are fully crusted and dry. While covering the lesions can offer a physical barrier, the primary preventative measure remains the rapid and consistent use of antiviral therapy to halt viral replication.