Ringworm

Ringworm, or dermatophytosis, is a common fungal infection of the skin, hair, or nails caused by dermatophyte fungi such as Trichophyton, Microsporum, and Epidermophyton. The name ringworm is historical and misleading—there are no worms. Infections are named by site: tinea corporis (body), tinea capitis (scalp), tinea pedis (foot), tinea cruris (groin), and tinea unguium (nails).

Transmission typically occurs through direct skin-to-skin contact with an infected person or animal, or via contaminated objects and surfaces. The infection often presents with red, scaly patches that may itch, sometimes with a ring-like border and a clearer center. Hair loss can occur with scalp infections, and nails may become thickened or discolored. In some cases, infections are mild and asymptomatic.

Diagnosis is usually clinical, supported by microscopy of skin scrapings using a potassium hydroxide preparation or by fungal culture. Most skin infections respond to topical antifungals such as terbinafine or azoles applied daily for 2–4 weeks. More extensive disease, scalp involvement, or nail infection often requires systemic antifungals (for example, terbinafine, itraconazole, or fluconazole) for several weeks to months. Avoid stopping treatment early to reduce recurrence, and monitor for adverse effects when using oral therapy.

Prevention includes keeping skin clean and dry, not sharing towels or personal items, and treating infected pets. Ringworm is contagious, and recurrences are common if risk factors persist; prognosis is generally good with appropriate treatment. If symptoms worsen or fail to improve, consult a healthcare professional.