We appreciate the comments of Dr Rietschel on his experience with patients who had a clinical presentation of urticarial dermatitis and patch test results that were negative for contact allergens.
The term urticarial dermatitis may not be an oxymoron as we do not consider the reaction pattern to be simply due to the combination of physical or allergic urticaria combined with dermatitis but rather to be a genuine reaction pathway. The urticarial appearance may reflect the presence of T cells with a helper type 2 phenotype-producing cytokine (eg, interleukin [IL] 4, IL-5, and IL-10) that may induce eosinophilia and urticarial reactions. There is initial evidence, not only in reports of atopic dermatitis1 but also of systemic contact allergies2 and pemphigoid gestationis,3 that T-helper type 2 lymphocyte mediators can be demonstrated in each of these conditions that may present clinically as urticarial dermatitis.
Kossard S, Hamann I. A Clinician's View of Urticarial Dermatitis—Reply. Arch Dermatol. 2006;142(7):927-947. doi:10.1001/archderm.142.7.932-b