A 38-Year-Old Dog Owner With a Blistering, Itchy Rash

Melba Estrella, MD; Alan Snyder; John Plante; Dirk M. Elston, MD

Disclosures

October 29, 2020

Discussion

Herpes simplex virus infection can affect almost any area of the skin or mucous membranes and presents with localized blistering. Isolation of the virus in tissue culture confirms the diagnosis.[1] In this case, the viral and bacterial cultures were negative. Although atopic dermatitis can occur on any part of the body, it would not remain as focal and symmetric over time, as the eruption seen in this patient has been—with the exception of flexural presentations, which were not observed in this case.

Plaque psoriasis may cause large, itchy, and erythematous demarcated scaly plaques confined to areas of pressure. However, in contrast to the thin scaling on this patient's plaques and mild edema, psoriasis displays bumpy red plaques with silvery thick scales that when removed elicit pinpoint bleeding, commonly known as the Auspitz sign. The punctate erosions in this case could potentially resemble the remnants of pinpoint bleeding, but because they were formed in the presence of vesiculation, it would be extremely unlikely for this presentation to be psoriasis. Thus, contact dermatitis is the diagnosis of exclusion.

Contact dermatitis is an inflammatory response of the skin to environmental insults that acutely manifests with pruritic skin lesions and varying degrees of erythema, edema, scaling, and vesicles. Contact dermatitis may be classified as allergic or irritant. Allergic contact dermatitis is a delayed type of hypersensitivity reaction induced by a lymphocyte-mediated response after skin contact with sensitized allergens.[2] Irritant contact dermatitis is a non–immune-mediated inflammatory response by mediators of epidermal cells that react to direct chemical insults on the skin. Because allergic and irritant contact dermatitis often overlap in clinical presentations, identifying the correct trigger of the reaction is essential.

The linear distribution of the rash in this case strongly suggests a reaction to the elastic waistband of the patient's underwear. Rubber-containing products, such as elastic waistbands, can be associated with bleached rubber syndrome, conventional allergic contact dermatitis to rubber antioxidants and accelerators, and even irritant dermatitis.[2] No reliable diagnostic tests for irritant contact dermatitis are available; thus, the diagnosis in this case relies mainly on the exclusion of allergic contact dermatitis and appropriate clinical interventions.[3]

For reasons not yet clearly understood, many patients can become sensitized to certain components found in the molecules of natural rubber (latex) or synthetic rubber; however, they are more likely to become sensitized to the many chemicals used in the process of rubber manufacturing. These chemicals make up a wide list of allergens ranging from vulcanizing to accelerator agents; the latter is the most common of these allergens. A detailed list of these chemicals is available at DermNet NZ.[4] About 1%-5% of the general population exhibits rubber allergy as a reaction either to the components of rubber or to its manufacturing resins.[2]

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