Trichophytid is a secondary, allergic, inflammatory response of the skin to the dermatophyte infections.
The primary infections are mostly caused by zoophilic fungi, with strong inflammatory reactions, predominantly in kerion and intertriginous or vesicular tinea pedis. Trichophyton schoenleinii can also cause trichophytid. Local fungal metabolites are antigenic, causing allergic reactions in the whole body and local skin after dissemination in blood. In the secondary rash, fungal test is negative and trichophyton test is positive. With the healing of primary, focal, fungal infections, the rash gradually subsides.
Signs and Symptoms
Erythema, papules, and vesicles occur suddenly on the skin surrounding or remote to the active primary lesion, often with pruritus, mainly on the palms, lateral fingers, feet, and calves. Skin lesions are mainly pea sized blisters, with thick wall, resembling those of pompholyx or contact dermatitis, with severe pruritus, mainly caused by tinea pedis. If secondary bacterial infections occur, pain may be present. Skin lesions mainly composed of papules are scattered or clustered, mostly on the extremities, rarely on the trunk. Some patients have fever and general malaise, which are often caused by tinea capitis. In addition, skin lesions mostly consisting of erythema resemble those of erysipelas, erythema annulare centrifugum, and erythema nodosum, and are often localized to the calves.
Figure 1 trichophytid on the palms
Figure 2 trichophytid on the dorsal hands
Figure 3 trichophytid on the dorsal feet
On the basis of clinical presentations, positive fungal examination in the primary lesions, and positive trichophyton test, the disease can be diagnosed.
Astringent hydropathic compresses, such as 2% - 3% plumbic acetate solution, copper sulfate solution, and 2% boric acid solution, and astringent lotions, creams, emulsions, and pastes can be considered.
Patients with systemic symptoms can take antihistamines orally, and corticosteroids can be added in severe cases. Calcium, vitamin C, and procaine blocking can also be used. Primary fungal infections should be treated with systemic itraconazole, fluconazole, and terbinafine if necessary.