Abstract
Demodex mites are commonly found in the healthy population, but the pathogenesis of demodicidosis has still not been clarified, though it is usually found in cases of immune deficiency. A 45-year-old man presented with an unusual outbreak of erythema and swelling 6 months after resection and chemoradiotherapy for a squamous cell carcinoma of the anterior floor of the mouth. The cheek was biopsied and histological examination showed demodicidosis. In cases of erythema with a normal blood cell count and no history of allergy, particularly in patients with reduced immunity, demodicidosis should be considered as a diagnosis and should be confirmed by examination of a biopsy specimen.