From the Guidelines
An ID reaction, also known as dermatophytid, is a cell-mediated host response to a dermatophyte infection that can occur after effective therapy has been initiated, and it does not warrant cessation of systemic antimycotic therapy. This reaction is characterized by a pruritic, papular eruption, particularly around the outer helix of the ear, and it should not be confused with a drug reaction 1. The ID reaction represents a delayed host inflammatory response to the causative dermatophyte, and it can be managed with topical or oral corticosteroids to provide symptomatic relief. Some key points to consider when managing an ID reaction include:
- The reaction is a secondary skin response that occurs at a site distant from the primary skin condition
- It typically presents as small, itchy papules that appear suddenly
- Common triggers include fungal infections, such as tinea capitis caused by zoophilic or endothrix species 1
- Treatment focuses on addressing the primary condition while managing the secondary eruption with topical corticosteroids and oral antihistamines for itching
- In severe cases, a short course of oral corticosteroids may be necessary The ID reaction usually resolves once the primary condition is treated effectively, and it demonstrates how localized skin conditions can cause systemic immune responses.
From the Research
ID Reaction Definition
- ID reactions are a type of secondary inflammatory reaction that develops from a remote localized immunological insult 2
- They can be caused by various fungal, bacterial, viral, and parasitic infections
Clinical Presentations
- ID reactions exhibit multiple clinical presentations, including:
- Localized or widespread vesicular lesions
- Maculopapular or scarlatiniform eruptions
- Erythema nodosum
- Erythema multiforme
- Erythema annulare centrifugum
- Sweet's syndrome
- Guttate psoriasis
- Autoimmune bullous disease 2
Treatment and Management
- The most important aspect of therapy involves the identification and adequate treatment of the underlying infection or dermatitis 2
- In some cases, oral antifungal therapy may exacerbate inflammatory reactions, and topical and/or systemic corticosteroids may be helpful in reducing these reactions 3
Antifungal Agents
- Terbinafine, itraconazole, and fluconazole are common antifungal agents used to treat fungal skin diseases 4, 5
- Combination therapy with terbinafine and itraconazole may achieve better therapeutic effects in fungal skin diseases 5
- Drug interactions should be considered when prescribing antifungal agents, and alternative agents may be used if necessary 4, 6