DermatologyPending review

Fungal skin infections

Dermatophyte fungi digest keratin in the stratum corneum and spread outward as they consume it, producing a scaly lesion with an actively advancing, inflamed edge and a clearing centre, the ring that gives ringworm its name.

First principles

Dermatophytes live on keratin, not living tissue

Dermatophyte fungi (Trichophyton, Microsporum and Epidermophyton species) secrete keratinases that digest keratin, and they can only infect dead keratinised structures (the stratum corneum, hair shafts and nails), not the living tissue beneath. This is why, in an immunocompetent host, infection stays confined to the superficial keratin layer rather than invading or causing systemic illness.

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Educational content pending clinical review. Not medical advice.