A generalized skin reaction associated with various infectious and inflammatory cutaneous conditions distant from the main rash of the disease:
- Id is a word termination often combined with a root reflecting the causative factor (ie, bacterid, syphilid, and tuberculid). The dermatophytid is the most frequently referenced id reaction in dermatology. A dermatophytid is an autosensitization reaction in which a secondary cutaneous reaction occurs at a site distant to a primary fungal infection. The eruption begins typically within 1–2 weeks of the onset of the main lesion or following exacerbation of the main lesion.
- System(s) affected: Skin/Exocrine
- Synonym(s): Dermatophytid, trichophytid, autoeczematization
- Predominant age: All ages
- Predominant sex: Male = Female
Unknown; no good data source
- Fungal infection of the skin
- Stasis dermatitis
- Minimize factors for developing fungal infections.
- Promptly treat any developing fungal infection.
Precise pathophysiology is uncertain. Circulating antigens may react with antibodies at sensitized areas of the skin, or abnormal immune recognition of autologous skin antigens may occur.
Commonly Associated Conditions
- Primary fungal infection
- Stasis dermatitis
Itchy rash: Assess for the primary fungal or bacterial lesions that would have preceded the onset of the id reaction by days to weeks.
- Symmetric, pruritic vesicles on the hands
- Tinea infection on the feet; contact or other eczematous dermatosis; or bacterial, fungal, or viral infection of the skin
- Generalized reactions can occur.
- Less common:
- Lichenoid eruption
- Eczematoid eruption
Diagnostic Tests & Interpretation
- Fungal infection at the primary site proven by potassium hydroxide (KOH) or fungal culture
- No fungal elements demonstrable at the site of the presumed id reaction
- Special tests: Skin shows a positive trichophyton reaction.
Follow-Up & Special Considerations
The id reaction resolves with successful eradication of the primary skin condition.
- Vesicles in the upper dermis
- Superficial perivascular lymphohistiocytic infiltrate
- Small numbers of eosinophils
- Moderate acanthosis
- Increased granular cell layer
- No infectious agents present in biopsy specimen
- Pompholyx (dyshidrotic eczema)
- Contact dermatitis
- Drug eruptions
- Pustular psoriasis
- Antihistamines for any pruritus
- Topical steroids for pruritus
- Systemic steroids only if reaction is severe or generalized
- Contraindications: Refer to manufacturer’s profile of each drug.
- Precautions: Refer to manufacturer’s profile of each drug.
- Significant possible interactions: Refer to manufacturer’s profile of each drug.
- Topical and/or systemic antifungals for identified associated fungal infection (common)
- Topical or systemic antibiotics for any secondary infection
- Appropriate health care: Outpatient
- Treatment of the underlying infection or eczematous dermatitis
- Symptomatic treatment of pruritus with antihistamines and/or topical steroids if needed (may require class 1 or 2 steroid)
- Treatment for secondary bacterial infection
Avoid hot, humid conditions that promote fungal growth. Aerate susceptible body areas (eg, wear sandals or open footwear). If possible, wear boxer shorts or loose-fitting clothing, dry off wet skin after bathing, and use powders and antiperspirants to make the environment less conducive to fungal growth. Treat primary dermatitis promptly.
After appropriate treatment, complete resolution in a few days to 2 weeks
Secondary bacterial infection (cellulitis)
1. Habif T. Clinical Dermatology, 4th ed. St. Louis: Mosby, 2004.
- 110.9 Dermatophytosis of unspecified site
- 692.89 Contact dermatitis and other eczema due to other specified agents
- 3014005 Id reaction (disorder)
- 30668009 allergy-sensitivity to fungi syndrome (disorder)
This is a diagnosis in the category of “If you don’t think of it, you won’t think of it,” so when you see one skin lesion follow another, think of the id reaction.