Erythema toxicum neonatorum, also known as urticaria neonatorum or erythema toxicum, is a common temporary dermatosis in newborns characterized by erythema, papules, and pustules.


Causes

The etiology is unknown. It is believed that the condition may be a non-specific reaction caused by external stimulations after birth, an allergic reaction caused by some antigenic substances from the mother’s body, a toxic reaction to intestinal substances, or a viral infection.


Signs and Symptoms

Erythema toxicum neonatorum occurs mostly within 4 days after birth, but also at birth or about 2 weeks after birth. Skin lesions are erythema, papules, wheals, and pustules. In some patients, there are initially diffuse erythema, followed by pinhead sized, yellowish white papules and pustules, with solid bases, with red halos, mostly scattered, occasionally fused. In addition to palms and soles, the condition can occur anywhere, but predominantly on the buttocks, back, and shoulders. The skin lesions vary in number. The skin lesions can regress within few hours and relapse soon without other systemic symptoms, and subside spontaneously within 7 - 10 days.

Figure 1 erythema toxicum neonatorum


Histopathology

There is mild edema in the upper dermis in the erythematous lesions, with mild infiltration of eosinophils, neutrophils and mononuclear cells around the blood vessels. Significant edema of the dermis can be seen in the early stage of papules, and the infiltration is mainly composed of eosinophils. The pustules are under the stratum corneum or in the pores or sweat pores of the epidermis, containing numerous eosinophils.


Diagnosis

On the basis of newborns with erythema, papules, wheals, and pustules, the condition should be considered.


Treatment

The condition is self limited, and there are not severe complications, so treatment is not required.