Bullous tinea pedis (athlete foot with blisters) can mimic bullous drug reactions, bullous pemphigoid, and other bullous diseases of the skin.
If suspected ringworm does not respond to routine antifungal treatment, further diagnostics must be performed, like a skin biopsy, a fungal culture, or a skin scraping for fungus identification.
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It would be advisable to consult a skin specialist for the symptoms and a proper clinical examination.
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