Erythema toxicum neonatorum (ETN) is a fairly common skin condition in newborns. It is both benign and self-limited. It occurs in the early neonatal period, that is, in the period from birth to one month, and typically between days 2 to 5.
It is characterized by the appearance of red blotchy spots on the skin, with whitish-yellow papules or pustules overlying them.
Also known as toxic erythema of the newborn, or urticaria neonatorum, ETN affects up to nearly half of all full-term infants. It is, however, found to occur much less frequently in those infants who are born prematurely.
There is no known gender or racial predilection associated with ETN. The incidence may be falsely low in children with darker skin due to under-recognition of the condition.
ETN may appear frightening to the new parent, but it is thought to cause no discomfort to the baby. The number of lesions may range from few to numerous, but all usually resolve within the first two weeks.
ETN most frequently begins on the face and spreads in descending manner, to affect the trunk and the limbs. It usually spares the palms of the hands and the soles of the feet. When lesions are few, they typically resolve within a few hours.
It is unusual for individual lesions to last for more than 24 hours. Despite the fears of the parents of the infant affected, the newborn is usually not sick even when the rashes appear to be extensive.
Pathophysiology
Activation of the immune system has been implicated as a potential cause of ETN. This suggestion has been made on the basis of finding increased levels of inflammatory and immunological markers, such as interleukin-1, interleukin-8, the adhesion molecule E-selectin, eotaxin, the chemotactic factor psoriasin and nitric oxide, among others.
ETN predominantly affects the hair-bearing areas of the skin, and this suggests the potential involvement of the hair follicle. This seems to be supported by the observed increase in the number of mast cells around the hair follicles.
Although no allergens have been identified, there is an eosinophilic infiltrate in the affected areas of skin in ETN. This indicates the possibility of a hypersensitivity- or allergy-related etiology.
The skin of a neonate typically responds to any insult with eosinophilic aggregation.
The finding that premature infants are less commonly affected by ETN has led some to believe that immunological maturity is required to generate the reaction in the newborn baby.
Contact and mechanical irritation have both been ruled out as potential etiologies for toxic erythema of the newborn.
Treatment and prognosis
The diagnosis of ETN is usually made on clinical grounds. Histological tests done from skin biopsies may show inflammatory cell and eosinophilic infiltrates, but this is not required.
Although ETN does not require any treatment owing to its benign nature, it is imperative to rule out other differential diagnoses such as infections.
The use of lotions to treat the rash, excessive or too vigorous washing of the baby, or rubbing or breaking the pustules associated with ETN should be scrupulously avoided, to prevent secondary skin infections.
The parents should be reassured that they can leave the condition to resolve on its own, as it usually does.
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