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Erythema toxicum neonatorum (ETN) only occurs in the newborn. It has the appearance of small, erythematous papules and vesicles. Occasionally pustules also occur. The lesions are often surrounded by areas of diffuse blotchy erythema, giving the appearance of a distinct halo. Individual lesions are quite transient and usually disappear quickly, only to be replaced by others in different parts of the body. The condition is benign, causes no symptoms and resolves spontaneously.
The condition has been known throughout the ages and was described by ancient Mesopotamian physicians. The exact cause is not known but some authorities have attributed it to an allergy because of the prominence of eosinophils within the lesions. Some popular theories include:
- An immune system reaction involving hair follicles (the condition normally occurs on hair-bearing areas and clusters of mast cells can be seen around hair follicles).
- An innate immune response against commensal colonisation by organisms such as Group B streptococcus.
- Over-expression of high mobility group box chromosomal protein 1 (HMGP-1), a proinflammatory cytokine released by macrophages and keratinocytes.
- A transient adjustment reaction of the newborn skin to mechanical or thermal stimulation.
- Caucasian race.
- Higher birth weight.
- Greater gestational age.
- Maternal age less than 30 years.
- Male gender.
- Term birth.
- Fewer than two pregnancies.
- The birth season (higher in summer and autumn).
- Feeding with milk powder substitute or a mixed diet.
- The length of labour in vaginal delivery.
The typical rash appears in newborns between the ages of 3 days to 2 weeks. Rarely, it can occur within the first 48 hours. The transience of the lesions is characteristic; they can appear or disappear within minutes to hours.
- The characteristic appearance of the lesions, their fleeting nature and the lack of systemic features makes the condition fairly easy to diagnose clinically.
- If the clinical picture is atypical, material taken from a pustule should be examined to exclude bacterial, viral and fungal infections.
- A peripheral blood film may show eosinophilia.
- If systemic sepsis is suspected, blood cultures should be taken to exclude Group B streptococcus, Listeria spp., Escherichia coli and other pathogens.
- If necessary, a skin biopsy should be taken. Typically, there is accumulation of primary eosinophils. Other features may be neutrophils in the follicular epithelium, hyperkeratosis and follicular plugging.
The condition is self-limiting and requires no treatment. Parents should be reassured about this but advised to report any atypical features.
No complications occur. Despite the presence of eosinophils within the lesions, no links to atopic conditions have been established.
Full resolution is expected within two weeks of onset. 11% of patients develop a recurrence six weeks later.
Further reading & references
- Erythema Toxicum Neonatorum; Skinsight
- Mahajan VK, Sharma NL; Erythema toxicum neonatorum. Indian Pediatr. 2010 Sep;47(9):793.
- Morgan AJ et al; Erythema toxicum neonatorum revisited, Cutis. 2009 Jan;83(1):13-6.
- Marchini G, Stabi B, Kankes K, et al; AQP1 and AQP3, psoriasin, and nitric oxide synthases 1-3 are inflammatory mediators in erythema toxicum neonatorum. Pediatr Dermatol. 2003 Sep-Oct;20(5):377-84.
- Yamasaki O, Manabe K, Morimoto A, et al; Pustular erythema toxicum neonatorum in two siblings born to a mother with group B streptococcus colonization. Eur J Dermatol. 2011 Mar-Apr;21(2):271-2. doi: 10.1684/ejd.2010.1229.
- Monteagudo B, Labandeira J, Cabanillas M, et al; Prospective study of erythema toxicum neonatorum: epidemiology and predisposing factors. Pediatr Dermatol. 2012 Mar-Apr;29(2):166-8. doi: 10.1111/j.1525-1470.2011.01536.x. Epub 2011 Nov 8.
- Liu C, Feng J, Qu R, et al; Epidemiologic study of the predisposing factors in erythema toxicum neonatorum. Dermatology. 2005;210(4):269-72.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Laurence Knott
Dr Laurence Knott
Dr Helen Huins