The primary lesion is the wheal, a whitish-to-reddish, well-demarcated, edematous papule or plaque with a
pale center. This is usually surrounded by a halo and quite pruritic. Wheals may be linear, round, oval,
annular, arcuate, serpiginous, or generalized. They vary from several millimeters to 10 cm, affecting mostly
the trunk, buttocks, and chest, although they also can occur anywhere. They last from minutes to hours,
always resolving with no post inflammatory pigmentary changes or scaling. If individual lesions last longer than a day (and are associated with pigmentary changes or symptoms other than pruritus—such as pain or
burning), consider performing a biopsy to exclude urticarial vasculitis, a forme fruste of leukocytoclastic
vasculitis that may be associated with internal organ involvement.
pale center. This is usually surrounded by a halo and quite pruritic. Wheals may be linear, round, oval,
annular, arcuate, serpiginous, or generalized. They vary from several millimeters to 10 cm, affecting mostly
the trunk, buttocks, and chest, although they also can occur anywhere. They last from minutes to hours,
always resolving with no post inflammatory pigmentary changes or scaling. If individual lesions last longer than a day (and are associated with pigmentary changes or symptoms other than pruritus—such as pain or
burning), consider performing a biopsy to exclude urticarial vasculitis, a forme fruste of leukocytoclastic
vasculitis that may be associated with internal organ involvement.