History
Id reactions result from a variety of stimuli, including infectious entities and inflammatory skin conditions. Dermatological manifestations vary and depend on the etiology of the eruption. General history may include the following:
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Varying degrees of pruritus are typically noted.
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An acute onset of an extremely pruritic, erythematous, morbilliform, or papulovesicular eruption occurs 1-2 weeks after primary infection or dermatitis. Id reactions associated with stasis dermatitis are usually symmetrical and, in descending order of frequency, involve the forearms, thighs, legs, trunk, face, hands, neck, and feet.
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Id reactions are usually preceded by exacerbation of the preexisting dermatitis induced by infection, scratching, or inappropriate therapy. (Id reaction to tinea incognito has been reported. [19] )
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Reactions have previously been reported after radiation treatment of tinea capitis.
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Vesicles may be present on the hands or feet.
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Fingers may be tender.
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Travel history relating to infectious agent exposure may be relevant.
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A history of cultural or religious practices may indicate possible contact allergens leading to an id reaction.
Physical Examination
Clinical lesions of id reactions are quite variable and are largely predicated on the inciting etiology. Lesions are, by definition, at a site distant from the primary infection or dermatitis. They are usually distributed symmetrically. Clinical forms include the following:
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A widespread, symmetrical eruption of small follicular papules associated with a kerion and a pompholyxlike eruption are usually associated with inflammatory tinea pedis (common). [20]
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An acute, intensely pruritic, symmetric maculopapular or papulovesicular reaction that involves the forearms, thighs, legs, trunk, face, hands, neck, and feet (in descending order of frequency) is typical of the id reaction with stasis dermatitis (common).
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Erysipelaslike eruption on the anterior leg secondary to a dermatophytosis may occur (less common).
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Extracutaneous manifestations include fever, anorexia, generalized adenopathy, splenomegaly, and leukocytosis (uncommon).
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The clinical picture may rarely mimic erythema multiforme. [21]
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Id reaction (autoeczematization). Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/dermatitis/a-ecz2.jpg).
