Herpes Simplex Virus

Herpes simplex virus is the virus behind cold sores. Type 1 (HSV-1) causes most cases of Eczema Herpeticum, usually during a child’s first infection, 5–12 days after contact with someone who may have no visible cold sore. In toddlers with Atopic Dermatitis it can spread rapidly across eczema skin and needs immediate Aciclovir (DermNet 2023; NICE QS44). After the first infection the virus stays latent in sensory nerves for life. It can reactivate as recurrent cold sores, triggered by illness or sunlight (DermNet HSV; NHS).

Herpes Simplex Virus [causes] Eczema Herpeticum Atopic Dermatitis [worsens] Eczema Herpeticum Aciclovir [treats] Herpes Simplex Virus

How toddlers catch it. Primary HSV-1 infection “occur[s] mainly in infants and young children”. In crowded settings nearly all children are infected by age 5, but in the UK fewer than half of university entrants have been (DermNet HSV). The NHS says most people catch it in childhood “after close skin to skin contact, such as kissing, with someone who has a cold sore”. HSV spreads by direct or indirect contact with an active lesion, which is infectious for 7–12 days. Shedding in saliva without symptoms can also transmit it, but less often, because inactive sites shed 100–1000 times less virus. The incubation period is 2–12 days. Toddlers also spread it to themselves: a thumb-sucker can carry virus from mouth to thumb (DermNet HSV). In children aged 1–5, the first infection often shows as Herpetic Gingivostomatitis: fever, drooling, painful swollen gums and mouth ulcers.

Herpes Simplex Virus [causes] Herpetic Gingivostomatitis Herpetic Gingivostomatitis [precedes] Eczema Herpeticum

Conflict: [DermNet Eczema herpeticum, 2023-05] stresses that eczema herpeticum often follows contact with someone “who may have no visible cold sore”. [DermNet Herpes simplex, n.d.] says asymptomatic shedding transmission “is infrequent”. [NHS Cold sores, 2024-02] frames contagiousness as running from first tingling until full healing. How much protection families get from avoiding only visible cold sores is unresolved — add to open_questions.

Prevention advice for families. The NHS says cold sores are contagious “from the moment you first feel tingling” until “completely healed”. Its advice: do not kiss anyone while you have a cold sore, wash hands whenever you touch it, and never kiss a baby with a cold sore (risk of Neonatal Herpes). For a toddler with eczema, the practical steps are:

• Relatives and carers with a cold sore, or the tingle of one coming, should not kiss the child’s face or broken skin.
• Avoid sharing cups, spoons and towels during an outbreak.
• Wash hands before applying emollients.
• Keep eczema controlled, since active eczema gives the virus more broken skin to spread across (DermNet 2023).

UKHSA sets no nursery exclusion for cold sores, so a toddler may share a room with children who have them. Parents should know the warning signs: rapidly worsening painful eczema, clusters of blisters or uniform 1–3 mm punched-out erosions, fever or lethargy. These need same-day assessment (NICE QS44; NHS).

Herpes Simplex Virus [triggers] Eczema Herpeticum Emollient Therapy [prevents] Eczema Herpeticum

Medicines that raise risk. Some eczema medicines carry herpes warnings. JAK Inhibitors list herpes infections in their boxed warning. The US Dupilumab label warns of oral herpes and other HSV infections. Topical Calcineurin Inhibitors should not be applied to skin with cold sores or suspected eczema herpeticum. Topical Corticosteroids are now considered safe to continue during eczema herpeticum (DermNet 2023; Aronson 2011).

JAK Inhibitors [relates] Herpes Simplex Virus Dupilumab [relates] Herpes Simplex Virus

Connections

• Eczema Herpeticum — causative agent, source: DermNet 2023
• Infected Eczema — viral cause of infected eczema, source: NICE NG190
• Aciclovir — antiviral treatment, source: NICE QS44; DermNet
• Herpetic Gingivostomatitis — typical primary infection at ages 1–5, source: DermNet HSV
• Neonatal Herpes — risk from kissing babies with cold sores, source: NHS Cold sores
• Impetigo — look-alike crusted sores; differential diagnosis, source: NHS; NICE NG153
• JAK Inhibitors — herpes infection warnings, source: vault note
• Dupilumab — label warns of oral herpes/HSV infections, source: vault note (US label)
• Topical Calcineurin Inhibitors — not on skin with cold sores, source: vault note
• Atopic Dermatitis — eczema skin allows rapid HSV spread, source: DermNet 2023