Ringworm

Overview

Ringworm (tinea) is a fungal skin infection, not caused by a worm. It produces a characteristic ring-shaped, red, scaly, and itchy rash that spreads outward from a clear centre. Different types affect different body areas: tinea corporis (body), tinea capitis (scalp), tinea cruris (groin, also called jock itch), and tinea pedis (feet, also called athlete's foot).

How common is it?

Ringworm is common worldwide. CDC estimates that up to 25% of people may experience it during their lifetime. Scalp ringworm is particularly common in children; frequency varies by region and infection site.

Causes and risk factors

Dermatophyte fungi (Trichophyton, Microsporum, Epidermophyton species) infect keratin in skin, hair, and nails, living on the outer layers without invading deeper tissues.

Common risk factors

• Contact with infected person, animal, soil, or shared items (towels, combs, sports equipment)
• Warm, humid conditions promoting fungal growth
• Participation in contact sports (wrestling, football)
• Walking barefoot in communal areas
• Excessive sweating
• Weakened immune system or diabetes
• Close contact with infected pets (especially cats)

Symptoms

• Scaly, often ring-shaped patches that may be red or darker than surrounding skin; colour changes can be less obvious on brown or black skin.
• Itching at the affected site
• Scalp: scaly patches with hair loss, sometimes with pustules (kerion)
• Groin: red, itchy rash in the groin folds
• Feet: scaling, maceration between toes, itching, sometimes blisters (athlete's foot)
• Nails: thickened, discoloured, crumbling

When to see a doctor

See a clinician for scalp or suspected nail infection, diabetes, a weakened immune system, or failure to improve after the recommended antifungal course. Seek prompt assessment for painful swelling, pus, fever or spreading inflammation.

Diagnosis

Usually clinical. Skin scraping or hair/nail sampling sent for microscopy and culture if uncertain. Scalp ringworm may fluoresce green under Wood's lamp for some species.

Treatments

Self-care and lifestyle

• Do not share towels, hairbrushes, or combs with infected individuals
• Treat infected pets promptly (veterinary advice)
• Keep affected skin dry and well ventilated
• Let the school or nursery know about scalp ringworm and follow local attendance advice. Ask the clinician which close contacts need checking; do not assume every classmate needs screening.

Prevention

Avoid contact with infected animals and people. Wear flip-flops in communal areas. Keep skin dry. Treat athlete's foot promptly to prevent nail spread.