Tinea Cruris

Key facts

• Tinea cruris, commonly called jock itch, is a superficial fungal infection affecting the groin, inner thighs, and sometimes the buttocks.
• Warm, humid conditions and sweat trapped under clothing let the dermatophyte fungi that cause it thrive in moist skin folds.
• A well-defined, ring-shaped red rash with a scaly or raised border is typical, and it usually spares the scrotum, which helps distinguish it from other groin conditions.
• Topical antifungals such as terbinafine usually clear the infection within one to two weeks.

What drives the rash

The infection is caused by dermatophyte fungi that thrive in moist, confined skin folds. Warm, humid weather and sweat trapped under clothing create ideal conditions for it, which is why it flares more in hot weather and with tight or damp clothing. A well-defined, ring-shaped red rash with a scaly or raised border is characteristic; it typically spares the scrotum, which helps distinguish tinea cruris from other groin conditions.

Clearing the infection

Antifungal treatment applied directly to the skin is the standard approach. Terbinafine works by disrupting the fungal cell membrane and usually clears the infection within one to two weeks of consistent use. Keeping the area clean and dry, wearing loose breathable fabrics, and changing out of damp clothing promptly all reduce the chance of recurrence.

When to see a doctor

See a doctor if the rash spreads beyond the groin, involves the feet as well (tinea pedis is a common co-infection), or fails to improve after two weeks of treatment.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.